Inventions 

'O speculators about perpetual motion, how many vain chimeras have you created in the like quest? 
Go and take your place with the seekers after gold.' 

[With drawing] 
Method of drying up the marsh at Piombino. c.a. 139 r. c 

[Diagrams] 

Here there is need of a clock to show the hours, minutes and seconds (I' ore punti e minuti). 

For measuring how great a distance one goes in an hour with the current of the wind. 

For learning the quality and density of the air and when it will rain. 

For reckoning the mileage of the sea. c.a. 249 v. a 

[With drawing] 

This is the way to dredge a harbour, and the plough m n will have in front of it spikes shaped like ploughshares and knives, and this plough will be used to load a large cart with mud. The cart will have its back perforated after the manner of a net in order that the water may not be shut within the box; and the said plough is to be moved along above the place where the mud is to be dug out, and along with it a barge; and when it has reached the bottom the windlass b will draw it underneath the windlass a, and the windlass a will raise it up when it is full as far as its beam, in such a way that there will be room for the barge to go underneath it and take the mud from the plough; and so this plough will be able to dislodge the mud from the bottom and unload it upon the barge which is placed underneath it. 

c.a. 307 r. b 

Make to-morrow out of various shapes of cardboard figures descending through the air, falling from our jetty; and then draw the figures and the movements made by the descent of each, in various parts of its descent. c.a. 375 r. c 

[With drawings] 

These scissors open and shut with a single movement of the hand. 

Scissors used by the bonnet-makers for cutting cloth. Rapid in the action of opening and shutting like the others. 

This [tool I has in itself so much more ease in its movement because the user does not have to adjust the spring or curve, as is the case with those scissors which are all in one piece. With these it is not necessary to wait in order to cut the threads of the cloth, or to bend by force the spring which is in the heel of the scissors. 

This closes at the same rate of speed as the rest; but opens much more rapidly. c.a. 397 v. a 

[Drawing of apparatus with ropes and pulleys] 

Method of raising and lowering the curtains of the treasures of sil- 
ver of the lord. Tr. 6 a 

[With drawing of tube descending from surface of water to cover 
mouth of man in diving dress] 
This instrument is employed in the Indian Ocean in pearl fishing; 
it is made of leather with numerous rings so that the sea may not 
close it up. And the companion stands above in the boat watching, 
and this [diver] fishes for pearls and corals, and he has goggles of 
frosted glass and a cuirass with spikes set in front of it. b 18 r. 

A WAY OF SAVING ONESELF IN A TEMPEST OR 
SHIPWRECK AT SEA 

[With drawing] 

It is necessary to have a coat made of leather with a double hem 
over the breast of the width of a finger, and double also from the girdle 
to the knee, and let the leather of which it is made be quite air-tight. 
And when you are obliged to jump into the sea, blow out the lappets 
of the coat through the hems of the breast, and then jump into the sea. 

And let yourself be carried by the waves, if there is no shore near at 
hand and you do not know the sea. 

 

792 INVENTIONS 

And always keep in your mouth the end of the tube through which 
the air passes into the garment; and if once or twice it should become 
necessary for you to take a breath when the foam prevents you, draw 
it through the mouth of the tube from the air within the coat. 

b 81 v. 
[Alaritm-clocl(\ [With drawing] 

A clock to be used by those who grudge the wasting of time. 

And this is how it works: — when as much water has been poured 
through the funnel into the receiver as there is in the opposite balance 
this balance rises and pours its water into the first receiver; and this 
being doubled in weight jerks violently upwards the feet of the sleeper, 
who is thus awakened and goes to his work. b 20 v. 

[Drilling machine] 

In order to drill through a beam it is necessary to hold it suspended 
and drill from below upwards so that the hole may empty of itself, and 
you should make this canopy so that the sawdust may not fall upon 
the head of him who turns the screw; and see that the turners rise at 
the same time as the said screw. And make the hole first with a fine 
auger and then with a larger one. b 47 v. 

[Drawing] 

A sledge for use in mud. And make the part that comes upon the 
ground united in order that it may not get stuck in the mud. 

b 49 v. 
[Drawing] 

A sledge for use in mountainous and rocky places. And do not make 
the part that touches the ground united, so that it may be less difficult 
to drag; for the less the weight touches the less difficult it is to move. 

b 50 r. 
[Timepiece. With drawing] 

Four springs for a timepiece, so that when one has finished its course 
the other commences, and as the first turns the second remains 
motionless. And the first is fixed above the second like a screw, and 
when it is fixed the second spring takes the same movement com- 
pletely and so do all. b 50 v. 

[With drawing] [Paddle-boat] 
Barge made of beams and covered over above. But make a large 

 

INVENTIONS -,; 

wheel of oars concealed within it, and make a furrow from one end oi 
it to the other, as appears in a, where the wheel can touch the water. 

b 76 v. 
\To ma\e concrete} [With drawings] 

a is a box which can open and empty itself, and in it you can make 
a concrete formed of fine pebbles and chalk. Let these blocks dry on 
the ground and then place them one upon another under the water, 
in order to form a dam against the rush of the water. 

Frames filled with gravel and twigs of birch, that is a layer of twigs 
\sketch] placed vertically in this direction and a layer of gravel, then a 
layer in this contrary direction \s\etch] and then a layer of gravel, 
and thus you will construct it bit by bit. b 79 v. 

OF PROPORTION 

See if there are a number of small stones of different sizes whether 
the heaviest goes farthest when one throws it, then try alone with the 
same instrument and force, and see whether it travels a greater or less 
distance alone than when accompanied. And whether also if the stones 
are all of the same form and weight, like the balls of an air-gun, and 
are thrown by the same force in the same time they travel the same 
distance. 

BELLOWS WITHOUT LEATHER AND MERELY OF WOOD 

These bellows are like a sugar loaf and have a partition which 
divides them lengthwise in two parts. One — that is the upper part — is 
filled with water; that below is filled with air. The water falls down 
into the cubic space of the air through a small hole which is near the 
socket, and the increase of the water drives the air through the mouth 
of the bellows. Any scarcity of water in the upper part is filled by 
means of a valve which admits the air, and so also with the others; 
and this is the most serviceable type of bellows that can be used. 

 

Webbed glove for swimming in the sea. [With drawing] 

 

1 v. 

 

794 INVENTIONS 

[ Water bellows] [Drawings] 

These are kinds of bellows without leather and they are of admir- 
able utility and extremely durable. And their method of use is as 
follows: — The bellows is always from the centre downwards full of 
water, that is M N, and in the continual revolution of the bellows N 
rises until it reaches the air hole S T which is made in the outside of 
the second covering, as appears in the instrument below, and comes to 
meet with the said pipe S T the hole o which is in the reservoir N, 
and as much as is the volume of water that goes from N to M so 
much air enters through the hole o in the reservoir N, and as much 
air is driven out of the reservoir M as N gives it of water. And the 
air which is driven out from M by the water is that which blows the 
bellows. The said bellows should be of oak because this resists water 
for the longest time, and have inside it a coating of turpentine and 
pitch, so that when it is not in use the part above which is out of the 
water does not come to open; and this type of bellows is turned by the 
weight of a man walking above on the steps. 

It would also be extremely useful to cause it to turn by the force of 
a fall of water. 

The base of the bellows below the tube S T remains fixed, and the 
rest turns there within as a case would within its cover. 

Use salt water so that it may not become foul in the bellows. 

b 82 r. 
[With drawings of machine] 

To produce a marvellous wind. e 33 v. 

The current will be so much the more abundant as the small doors 
open with less descent, (discesa? MS. dissci . . .) 

The whole space of the small doors is equal to the whole space of 
the width of the pipe. e 34 r. 

 

MACHINE FOR EXCAVATING EARTH 

[Drawing] 

Here the calculation of the power is not at present fixed. 

But you, reader, have to understand that this has a use, which arises 
by means of the saving of time, which saving springs from the fact 

 

INVENTIONS 795 

that the instrument which conveys the earth up from below is always 
in the act of carrying it and never turns back. The adversary says that 
in this case it takes as long to turn round in a useless circle as to turn 
hack at the end of the forward action. But since the additional spaces 
of time that are interposed between the spaces of useful time are equal 
in this and in all other inventions, it is necessary to search here for a 
method whereby the time may be spent in as vigorous and effective 
a method of work as possible, which will be by inventing a machine 
that will take more earth; as wall be shown on the reverse of this page. 

The winch n as it turns causes a small wheel to revolve, and this 
small wheel turns the cogged wheel /, and this wheel / is joined to 
the angle of the boxes which carry the earth from the swamp and 
discharge themselves upon the barges. But the two cords m f and m b 
revolve round the pole /, and make the instrument move with the two 
barges against m, and these cords are very useful for this purpose. 

The pole is so made as to descend to as great a depth as the wheel 
has to descend in order to deepen the water of the marsh, e 75 v. 

As the attachment of the heavy body is further from the centre of 
the wheel the revolving movement of the wheel round its pivot will 
become more difficult although the motive power may not vary. 

The same is seen with the time of clocks, for, if you place the two 
weights nearer or farther away from the centre of the timepiece, you 
make the hours shorter or longer. f 7 v. 

[Magnifying glasses] 

Lens of crystal thickness, at the sides the twelfth part of an inch. 
This lens of crystal should be free from spots and very clear; and at 
the sides it ought to be the thickness of a twelfth of an inch, that is 
to say of the one hundred and forty-fourth part of a braccio, and thin 
in the centre according to the sight that it ought to serve for, that is 
to say according to the proportion of those lenses which agree with it; 
and let it be worked in the same mould as these lenses. The width of 
the frame will be one sixth of a braccio and its length one quarter of 
a braccio; consequently it will be three inches long and two wide, that 
is to say a square and a half. And this lens should be held at a distance 
of a third of a braccio from the eye when used, and it should be the 

 

796 INVENTIONS 

same distance from the letter that you are reading. If it is farther 
away this letter will appear larger, so that the ordinary type of print 
will seem like a letter on an apothecary's chest. 

This lens is suitable for keeping in a cabinet; but if you wish to keep 
it outside make it one eighth of a braccio long and one twelfth wide. 

f 25 r. 
[A pedometer'] \ Figure] 

In order to know how far one goes in an hour take the potter's wheel 
constructed as you see, and place above the instrument, of which the 
centre may be upon a circular line which turns exactly five braccia, 
the diameter being one and yf braccia. Then tightly close the instru- 
ment, have harmonic time, smear all the inside of the instrument with 
turpentine, turn the wheel uniformly and notice where the top layer 
of dust has stuck to the turpentine, and see how many revolutions 
the wheel has made and in how many beats of harmonic time. And 
if the wheel has made two revolutions in one beat of time, which 
amounts to ten braccia, that is to say the three-hundreth part of a mile, 
you will be able to say that this instrument has moved a mile in three 
hundred beats of time, and that an hour is one thousand and eighty 
beats of time; which will make three miles an hour and one hundred 
and eighty three-hundredth parts. f 48 v. 

[A decoration] 

If you make small pipes after the manner of goosequills, which are 
opaque and white with a coating of black within and then transparent, 
and with sardonyx outside and then transparent; and let all the thick 
portion of the pipes be made up of these mixtures, and then moisten 
them and press them and leave them to dry in the press; if you press 
them flat they will give one effect, if you press them into a rectangle 
they will give another and similarly if you press them into a triangle; 
but if you press them in front or folded in different ways you will also 
do well. 

And if in the transparent part exposed to the sun you make with a 
small style a mixture of different colours, especially of black and 
white opaque, and yellow of burnt orpiment, you can make very beau- 
tiful patterns and various small stains with lines like those of agate. 

f 55 v. 

 

INVENTIONS 797 

LAMP 

[Drawing] 

Lamp in which as the oil becomes low the wick rises. 

And this proceeds from the fact that the wheel which raises the 
wick rests upon the oil. As the oil diminishes so the wheel descends, 
and as it descends it revolves by means of the thread that is wrapped 
round its axle, and the cogs of the wheel push the toothed pipe that 
receives the wick. 

It will also do the same if a the axle of the wheel does not descend, 
and the only descent is that of the light object b which floats upon the 
oil, for this light object descends at the same time as the surface of 
the oil, and causes the wheel to turn, and this by means of its cogs 
pushes up the aforesaid cogged pipe with a slow movement. 

g 41 r. 

THE MINT OF ROME 

[With drawings] 

This can also be made without a spring, but the screw above must 
always be joined to the part of the movable sheath. 

No coins can be considered as good which have not the rim perfect; 
and in order to ensure the rim being perfect it is necessary first that 
the coins should be absolutely round. 

In order to make this it is necessary first to make the coin perfect 
in weight, breadth and thickness; therefore you must first have many 
plates made of this [uniform] breadth and thickness drawn through 
the same press, and these should remain in the form of strips, and 
from these strips you should stamp out the round coins after the man- 
ner in which sieves are made for chestnuts, and these coins are then 
stamped in the way described above. 

The hollow of the mould should be uniformly and imperceptibly 
higher at the top than at the bottom. 

This cuts the coins of perfect roundness, thickness and weight, and 
saves the man who cuts and weighs, and saves also the man who 
makes the coins round. 

They pass therefore merely through the hands of the worker of the 
plate and the stamper, and they are very fine coins. c 43 r. 

 

798 INVENTIONS 

OF PERCUSSION 

Among the accidental forces of nature, percussion greatly exceeds 
each of the others created by the motive powers of heavy bodies in 
equal time with equal movement, weight and force. This percussion 
is divided into simple and compound. Simple is that in which the 
motive power which is the striker is joined with the movable thing 
at its junction at the place struck; compound is that in which the 
movable thing as it strikes does not end its movement at the place of 
its impact, as does the hammer which strikes the die that stamps the 
coins. And this compound percussion is much weaker than simple 
percussion, for if the flat end of the head 1 of the hammer were to 
attach itself to the coin which it had to stamp and which it had struck 
upon the mould where was the impression, so that on this flat end 
of the head of the hammer there had been engraved the relief that 
was on the coin in reverse, the impression would be more definite and 
clear on the side struck with simple movement than on the side where 
the percussion is compound; as with the coin that remains struck in 
the die where the hammer has struck it in its descent, the percussion 
being reflected and thrown back against the front of the hammer. 

g 62 v. 

SIPHON CLOCK. SLOW TIME-FUSE 

[Of the siphon'] 

A preparation of mercury drawn through very fine copper of the 
shape of a siphon, the sides through the length of which the liquid 
rises and falls being of imperceptible thickness, will be seen to form 
a time-piece after the manner of an hourglass, and this is the slowest 
and most graduated descent that can be made, so much so that it may 
happen that in an hour not one grain of the mercury passes from one 
vessel to the other. 

And the surface of its container is sensitive by reason of the opacity 
of the mercury, the skin of this mercury becoming imperceptibly low- 
ered with the descent that occurs as the siphon discharges itself; and 
by this means you will be able to create a fire which by means of per- 

1 MS. bocha. 

 

INVENTIONS 799 

cussion will generate itself at the end of a year or more, and this with- 
out any sound down to the moment of the creation of the fire. 

And it is shown in the margin at the foot of the fourth page (folio 
48 r.) how one ought to fix or set up this vessel, which by the power 
observed gives the result which is promised us at the end. c 44 v. 

TO KNOW HOW FAR A SHIP TRAVELS IN AN HOUR 

The ancients have employed different methods in order to discover 
what distance a ship traverses in each hour. Among them is Vitruvius 
who expounds one in his work on architecture, but his method is falla- 
cious like the others. It consists of a wheel from a mill touching the 
ocean waves at its extremities, and by means of its complete revolutions 
describing a straight line which represents the line of the circumference 
of this wheel reduced to a condition of straightness. But this device is 
only of value on the smooth still surface of lakes; should the water 
move at the same time as the ship with an equal movement the wheel 
remains motionless; and if the movement of the water be either more 
or less swift than that of the ship, then the wheel will not have a move- 
ment equal to that of the ship, so that such an invention has but little 
value. 

Another method may be tested by experiment over a known distance 
from one island to another, and this is by the use of a light board which 
is struck by the wind, and which comes to slant to a greater or less 
degree as the wind that strikes it is swifter or less swift, and this is in 
Battista Alberti. 

As regards the method of Battista Alberti which is founded upon an 
experiment over a known distance from one island to another, such an 
invention will work successfully only with a ship similar to that with 
which the experiment has been tried, and it is necessary that it should 
be carried out with the same freight and the same extent of sail, and 
with the sail in the same position, and the waves of the same size. But 
my method serves with every kind of ship, whether it be with oars 
or sail; and whether it be small or large, narrow or long, high or low, 
it always serves. g 54 r. 

 

800 INVENTIONS 

[With drawing] 

KEY OF THE BATH OF THE DUCHESS 

Show all the ways of unlocking and releasing. Put them together in 
their chapter. i 28 v. 

BATH 

To warm the water of the stove of the duchess add three parts of 
warm water to four parts of cold water. 1 34 r. 

[With ground plan of Castle of Milan] 
A way of flooding the castle. 1 38 v. 

DRESS FOR CARNIVAL 

To make a beautiful garment take fine cloth and give it a strong- 
smelling coat of varnish made of oil of turpentine; and glaze it with 
eastern [scarlet] kermes, having the stencil perforated and moistened 
to prevent it from sticking. And let this stencil have a pattern of knots, 
which should afterwards be filled in with black millet, and the back- 
ground with white millet. 1 49 [1] v 

[With drawing] 

Water-clock which sounds twenty-four hours and the water falls 
half a braccio. 

Water-clock which shows the value [of time]. l 23 v. 

[With drawing] 
Water-clock. 

[With drawing of press] 
To press wine and oil in casks bound with iron. l 27 r. 

[Drawings] 
Machines for drying the trenches where the water has overflowed. 

l 69 v. 

 

INVENTIONS 80 1 

CAMP-BED 

[With sketch] 

Four straps for the length and eight across. 

And each of the straps to be buckled at one end and nailed at the 
other. , l 70 r. 

[Movable bridge] 
[Drawings] 

Bridge to draw horizontally with a windlass. 

Let a be a pulley b the windlass. 

c n will be a pavement of flagstones which has a tube beneath it 
through which the chain passes. 

This is the front of the said bridge. 

Here is a bridge which carries with it little wheels, and another, 
better, which travels on small wheels that remain fixed in one position. 

a b is the part of the bridge that projects out of the wall; b c is the 
part that remains within. m 55 v. 

[Fittings of a stove] 

This is the lattice which comes between the eyes and the fire of the 
stove. 

All the transparent part (il netto) has a breadth of a braccio and a 
quarter; and there are six thin boards but it is better that they should 
be of thin brass. 

The opening two braccia high and the transparent part one braccio 
and a quarter wide. 

You should divide it in height in two parts, so as to be able at will 
to open below and not above, in order to warm the legs. 

In the lower part you should use six boards, so that they are wider 
below than above in order to be able to put the feet to warm; above 
there should be eight, to be able to put the hands which are narrower. 

m 86 r. 
[Diagram ] 

To make a pair of compasses diminish or increase a portion of their 
measurement with equal proportion in each part. 

Bind it spirally with a screw which has as much of it smooth as en- 
ters in the compasses and all the rest is carved spirally; and this screw 

 

8o2 INVENTIONS 

may be changed at different places throughout the length of the com- 
passes, because at different places there are holes equally distant from 
the extremities of these compasses, into which the screw can enter 
halfway as at a, a quarter as at b, and one eighth as at c\ and so it 
proceeds through the whole, and it is bound by the nut h of this screw. 

Forster i 4 r. 

 

METHOD OF THE SMALL COMPARTMENTS OF THE ROUND 
MACHINE GIVEN BELOW 

[Drawing] 

Make it so that the buckets which are plunging with the mouth 
downwards have such an opening that the air cannot escape; it will 
also be a good thing that the covered exits to the buckets should be of 
terracotta so that they may be better able to pass beneath the water; 
and of copper would be best of all. Forster 1 50 v. 

[Sketch of loom] 

Threads for weaving ought to be two braccia long. 
[Sketch] 

Thus one ought to lay the warp. Forster 11 49 v. 

Moreover you might set yourself to prove that by equipping such 
a wheel with many balances, every part however small which turned 
over as the result of percussion would suddenly cause another balance 
to fall, and by this the wheel would stand in perpetual movement. 
But by this you would be deceiving yourself; for as there are these 
twelve pieces and only one moves to the percussion, and by this per- 
cussion the wheel may make such a movement as may be one twen- 
tieth part of its circle, if then you give it twenty-four balances the 
weight would be doubled and the proportion of the percussion of the 
descending weight diminished by half, and by this the half of the 
movement would be lessened; consequently if the first was one twen- 
tieth of the circle this second would be one fortieth, and it would 
always go in proportion, continuing to infinity. 

Forster 11 89 v. 

Whatever weight shall be fastened to the wheel, which weight may 

 

INVENTIONS 803 

be the cause of the movement of this wheel, without any doubt the 
centre of such weight will remain under the centre of its axis. 

And no instrument which turns on its axis that can be constructed 
by human ingenuity will be able to avoid this result. 

speculators about perpetual motion, how many vain chimeras have 
you created in the like quest? Go and take your place with the seekers 
after gold. Forster 11 92 v. 

[Diagram] 

To try again the wheel which continually revolves. 

1 have many weights attached to a wheel at various places : I ask you 
the centre of the whole sum of the weight. 

I take a wheel revolving on its axis, upon which are attached at 
various places weights of equal gravity, and I would wish to know 
which of these weights will remain lower than any of the others and 
at what stage it will stop. I will do as you see above, employing this 
rule for four sides of the circle, and that where you will see greater 
difference upon the arms of the balance, that is that experiment which 
will throw you the sum of one of the gravities more distant from the 
pole of the balance, that will go on and become stationary below; and 
if you want all the details repeat the experiment as many times as 
there are weights attached to the wheel. Forster 11 104 v. 

If you wish to make a boat or coracle strong, take . . . (allume 
splumie) and of these make fine cords and weave them together and 
do as one weaves the sacks after making oil of walnut, and of this 
cover your boat as you would with leather. Take from what is in the 
house, and test this by combing as with the sinew of the ox . . . 

Forster in 35 r. 

 

 


PAPER ON WHICH IT IS POSSIBLE TO DRAW IN BLACK 
WITH THE SALIVA 

Take dust of oak-apple and vitriol and reduce it to a fine powder 
and spread this over the paper after the manner of varnish; then write 
on it with a pen dipped in the saliva and it will become as black 
as ink. 

 

 

8o 4 INVENTIONS 

TO ADD WATER TO WHITE WINE AND SO CAUSE IT TO 

BECOME RED 

Crush an oak-apple to a fine powder and stand it for eight days in 
white wine, and in the same way dissolve vitriol in water, and let the 
water and the wine settle well and become clear each of itself, and 
strain them well; and when you dilute the white wine with this water 
it will turn red. Forster in 39 v. 

[S\etch] 

To weigh the force that goes to turn the millstone with its corn. 

Forster in 46 v. 
[S\etch] 
To measure a fall of water. Forster in 47 r. 

[Sketch] 

For taking away and placing in position rafters for the framework 
of houses and for their roofs. Forster in 56 v. 

[Sketch] [Self-closing gate] 
On one side is the shutter. Forster in 58 r. 

 

OF THE INSTRUMENT 

Anyone who spends one ducat for the pair may take the instrument, 
and he will not be paying more than half a ducat as a premium to 
the inventor of the instrument and one grosso for the operator; but 
I have no wish to be an under-official. Forster in 61 v. 

[With drawing] 

Dry or moist vapour-bath, very small and portable, weighing twenty- 
five pounds. Quaderni 11 9 v. 

[With drawings] 

A method of ascertaining how far water travels in an hour. This is 
done by means of harmonic time, and it could be done by a pulse if 
the time of its beat were uniform; but musical time is more reliable in 
such a case, for by means of it it is possible to calculate the distance 
that an object carried by this water travels in ten or twelve of these 

 

INVENTIONS 805 

beats of time; and by this means it is possible to make a general rule 
for every level canal. But not for rivers, for when these are flowing 
underneath the surface they do not seem to be moving above. 

Leic. 13 v. 
[Dratcing: with note 'lathe for potters'] 

How many miles an hour with a wind; and here one may see with 
the water of the mill which moves it how many revolutions the wheel 
which is about five braccia makes in an hour; and so you will make 
the true rule away from the sea, making the wheel go one, two, and 
then three times in the hour; and by this means you will regulate it 
exactly, and it will be true and good. Leic. 28 r. 

\ Meat-roasting jac\] 

Water which is blown through a small hole in a vessel in which it 
is boiled is blown out with fury and is entirely changed into steam, 
and by this means meat is turned to be roasted. Leic. 28 v. 

[Drawing: wheel on shaft with counterpoise on suspended looped cord] 
In order to see how many miles a ship can go in an hour have an 
instrument made which moves upon a smooth wheel together with 
this wheel, and so adjust the counterpoise that moves the wheel as to 
cause it to move for an hour; and you will be able to see how many 
revolutions this wheel makes in the hour. The revolution of the wheel 
may be five braccia, and it will make six hundred revolutions in a 
mile. And the glass should be varnished or soaped on the inside, so 
that the dust that falls from the hopper may attach itself to it; and the 
spot where it strikes will remain marked; and by this means you will 
see and be able with certainty [to discern] the exact height where the 
dust struck, because it will remain sticking there. Leic. 30 r.