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322 Review of Renwick 
To retain the valve in its position, the lever L, M, fig. 1, is fas- 
tened toa bar of iron, N, O, (supported by the uprights, N, P, and 
-O, R, of the same material) by a chain, which is attached to N, OQ, 
at one extremity, and which passing -round the lever, returns through 
an opening in N, O, tothe top of the bar, where it is secured by a 
padlock. In the drawing the area of the valve, I, K, is 44 square 
inches; this, at 150 Ibs. to the square inch, requires a weight of 675 
Ibs. to press it down. The short arm of the lever is 14 inch, the 
long arm 30 inches, the weight, T, is then about 33 lbs. 
-To raise the valve sufficiently above its seat, requires in the case 
figured, stanchions of 12.4 inches high. The whole apparatus thus 
occupies less than three feet in length, and eighteen inches in height. 
‘The dotted lines represent the position of the valve when, after the 
fusion of the plate, it may have been closed. 
sh 
Arr. XVI.—Treatise on the Steam Engine; by James RENWICK, 
LL.D, Professor of Natural Experimental Philosophy and Chem- 
_ istry, in Columbia College, New York. » New York: G. & C. & 
Hi. Carvill: 1830. pp. 328. 
Tue Steam Engine has become at the present day an object of 
intense .interest. The magnitude and variety of its performances 
awaken the highest admiration, while its resistless energies, trivmph- 
ing as they sometimes do over the ingenuity of man that controls all 
things else, inspire almost a superstitious awe and reverence. 42 the 
fabulous ages, men would have invested it with the attribute of di- 
vinity, and would have offered to it incense to propitiate its favors - 
The Steam Engine, moreover, affords the most striking’ exempli- 
- fication of the natural alliance which subsists between philosophy and 
the arts,—an alliance which, though it is so obvious to the present 
age, and so natural in itself that, as Professor Playfair remarks, what 
is a principle in science is a rule in art, was still scarcely dreamed of 
before it was pointed out by Lord Bacon. As this is the united and 
most noble production of both science and art, so no one is qualified 
to compose a treatise on it who is not a proficient im both. No other 
man can comprehend it in all its vast relations; no other can effectu- 
ally explore the causes of the dangers that still environ it; none cee 
with so much probability hope to find the means of obviating those 
dangers; none can judge so well of proposed improvements m 1S con- 
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