C04 MECHil 
upon the barrel, either at the top or bottom of the cellar, 
by turning of the winch K towards or from you, the barrel 
can be fafely and expeditioufly taken out or lowered down. 
When the crane is done with, it (huts up, by unfcrewing 
the hut at B, taking the wheel and axis away out of the 
loops at L, and folding the fides at A together, like a 
jointed rule; it may then be taken away in the cart or 
dray, or in the men’s hands. 
The crane reprefented at fig. 54.. was invented by Mr. 
Andrews, and weighs the body at the time that it is raif- 
ing it. The weight W is elevated by means of the levers 
M, N, O, P, which coil the rope H R round the barrel H. 
The jib ED Hands on a horizontal beam moveable in a 
vertical plane round the centre FA; and the diftance of 
the upright beam E from the centre of motion A is Jg of 
B F. The weight of the body W is then afcertained by 
the weight at B, which keeps it in equilibrio. The piece 
of wood C projefls from the vertical beam CT, in order 
to prevent the beam from rifing too high. This jib 
fhould be placed in the fame vertical plane with the part 
B A of the crane, at the time the weight is adjulled ; 
otherwife it will occafion a frifition which may prevent the 
■moveable beam from playing freely. For this invention 
Mr. Abraham Andrews, of Highain Ferrers, in North- 
amptonlhire, received from the Society for the Encourage¬ 
ment of Arts, a premium of fifteen guineas. 
Fig. 55. reprefents a portable machine for loading and 
unloading goods, by Mr. George Davis, of Windfor, 
Berks. A premium of forty guineas was given to Mr. 
Davis for this invention, by the Society of Arts, upon 
receiving a model thereof. The model was made on a 
fcale of about four inches to afoot, and would raife more 
than five hundred weight. The machine, therefore, when 
made of its intended fize, would no doubt be capable of 
loading a ton weight, by one man only ; and would be fo 
portable as not to exceed 112 lbs. in weight. A is the 
winch, which turns the bar B. This bar has on it two 
endlefs fcrews or worms, C, C, which work in the toothed 
wheels D, D. Thefe wheels are fixed to the barrels E, E, 
found which the ropes F, F, coil, wind up, or let out the 
fame occafionally; which ropes, palling over the two pul¬ 
leys G, G, are brought round; and their ends, having 
liooks for that purpofe, ^re hitched into fiaples, fixed to 
the front of the cart, or other carriage ; within thefe ropes 
the load H is placed at I, which forms an inclined plane, 
up which, by the turning of the winch, the ropes are 
ivound upon the barrels, and the load raifed into the car¬ 
riage. K K, the frame, intended to reprefent the part of 
the cart, or other carriage, on which the machine is occa¬ 
fionally to be placed. The whole of the barrels and cog¬ 
ged-wheels are contained in an iron box L, the fides of 
which are reprefented in the figure as taken off, that the 
eonflruHion of the feveral parts may be Ihown. 
Jacks. Plate XV. 
The common worm kitchen-jack exhibits the meeba- 
siical powers.in a familiar manner. Here the weight is the 
power applied, ailing by a fet of pulleys ; the friition of 
the parts, and the weight with which the fpit is charged, 
are the forces to be overcome ; and a Heady uniform mo¬ 
tion is maintained by means of a fly. This well-known 
machine is reprefented at fig. 56. A B C is the barrel, 
round which the cord QR is wound : K L the main wheel, 
commonly containing fixry teeth. N, the worm-wheel of 
about thirty teeth, cut obliquely. L M, the pinion, of 
about fifteen. O, the worm, or endlefs icrew, confiding 
of two fpiral threads, making an angle of fixty or feventy 
degrees with its axis. X the Hud, and Z the loop, of the 
worin-fpindle. P, a heavy wheel, or fly, connefled with 
the fpindle of the endlefs ferew to make the motion uni¬ 
form. D G, the Hruck wheel fixed to the axis FD. S, S, S, 
are holes in the frame, by which it may be nailed to a 
board, and thence to any wall, the end D being permitted 
to pals through it. II I, the handle, going upon the 
axis ET, to wind up the weight when it has run down. 
R is a box of fixed pulleys, and V a correfponding one of 
.NIC S. 
moveable pulleys carrying the weight. The axis ET is 
fixed in the barrel A C; which axis being hollow, both it 
and the barrel turn round upon the axis F D, which is 
fixed to the wheel K L, when it turns in the order B T A ; 
but cannot turn the contrary way, by reafon of a catch 
nailed to the end A B, which lays holds of the crofs-bars 
in the wheel LK. The weight, by means of the cord QR, 
in confequence of its defeent, carries about the barrel AB, 
which by the aftion of the catch carries the wheel K L, 
and this moves the pinion LM, and wheel N; the latter 
moving the worm O, and the fly P. Alfo the wheel LM 
carries the axis F D with the wheel D G, which carries 
the cord or chain that goes about the wheel or pulley at 
the head of the fpit. But, when the handle H gives mo¬ 
tion to the axis in a contrary order to that given by the 
weight, the catch is-depreffed ; fo that, although the bar¬ 
rel B C moves and winds the cord upon it, the wheel D G 
continues at refl. The time which the jack will continue 
in motion depends upon the number of pulleys at R and V ; 
and, as thefe increafe or decreafe, fo mull the weight which 
communicates the motion, in order to perform the fame 
work in the fame time. 
The fmoke-jack is an engine ufed for the fame purpofe 
as the common jack ; and is fo called from its being moved 
by means of the fmoke, or rarefied air, afeending the 
chimney, and finking againfi the machinery there placed. 
The fmoke-jack reprefented at fig. 57. is copied from Oza- 
nam’s Mathematical Recreations, edited by Montucla, 
and tranflated by Dr. Hutton. An iron bar, fixed in the 
back of the chimney, and projecting from it about afoot, 
ferves to lupporta perpendicular fpindle, the extremity of 
which turns in a cavity formed in the bar; while the 
other extremity is fitted into a collar in another bar, placed 
at fome diflance above the former. This fpindle is fur- 
rounded with a helix of tin plate, which makes a couple 
of revolutions or turns round the fpindle, and which is 
about a foot in breadth. But infiead of this helix, it will 
be fufiicient to cut feveral pieces of tin plate, orflieet iron, 
and to fix them to the fpindle in fucha manner that their 
planes fhall form with it an angle of about fixty degrees ; 
they mult be difpofed in feveral ftories, above each other ; 
fo that the upper ones may Hand over the vacuity left by 
the lower ones. The fpindle, towards its fummit, bears a 
horizontal wheel, the teeth of which turn a pinion having 
a horizontal axis; and the latter, at its extremity, is fur- 
niflied with a pulley, around which is rolled the endlefs 
chain that turns the fpit. Such is the confirutlion of 
this machine, the aftion of which may be explained in the 
following manner. When a fire is kindled in the chim¬ 
ney, the air which by its rarefaction immediately tends to 
afeend, meeting with the helicoid furface, or kind of in¬ 
clined vanes, caufes the fpindle, to which they are affixed, 
to turn round, and confequently communicates the fame 
motion to the fpit. The brifker the fire becomes, the 
quicker the machine moves, becaufe the air afeends with 
greater rapidity. When the machine is not ufed, it may 
be taken down, by railing the vertical fpindle a little, and 
removing the point from its cavity ; which will allow the 
fummit to be difengaged from the collar in which it is 
made to turn. When wanted for ufe, it may be put up 
with the fame eafe. 
The following mechanical amufement is founded cn 
the fame principle. Cut out from a card as large a circle 
as poflible; then cut in this circle a fpiral, making three 
or four revolutions, and ending at a fmall circle, referved 
around the centre, and of about a line or two in diameter ; 
extend this fpiral by railing the centre above the firfi re¬ 
volution, as if it were cut into a conical lurface or para- 
bolid ; then provide a fmall fpit made of iron, terminating 
in a point, and refiing on a fupporter. Apply the centre 
or fummit of the helix to this point; and, if the whole be 
placed on the top of a warm Hove, the machine will loon 
put itfelf in motion, and turn without the afiifiance of 
any apparent agent. The agent however in this cafe is 
the air, which is rarefied by the contaft of a warm body, 
and which afeending forms a current. There is no doubt 
3 that\ 
