340 Review of Allenh Mechanics. 



abandoned after a course of unsuccessful experiments, may be found' 

 collected as rubbish, forming a sort of museum of injudicious and 

 abortive contrivances." A book like the one before us, is calculated 

 to prevent the waste of property in this manner, by pointing out the 

 practical modes of success, and the common sources of failure. 



The first hundred pages are occupied with a consideration of mat- 

 ter as acted upon or modified by certain natural powers, as gravita- 

 tion, cohesion, magnetism, electricity, galvanism and heat, which ap- 

 pear to have most important effects upon all solid bodies, producing 

 changes in their gravity, strength, hardness, fluidity and forms. In 

 discussing these subjects, the author keeps constantly in view the de- 

 sign and object of his book, to wit, the application of science to the 

 arts, in a manner adapted to the capacities of manufacturers and me- 

 chanics, avoiding a pedantic display of technical terms and ostenta- 

 tious speculations, too often to be found in works of this kind, and 

 which embarrass the inquiries of those who are deficient in scientific 

 education. After a brief explanation o{ gravitation, he gives tables 

 and calculations for estimating the specific gravity of the substances 

 manufactured or used in manufactories, with directions for doing it 

 by admeasurement, by which the weight of sheets of malleable and 

 cast iron, of copper and lead, also, of square or round bars, of 

 ropes, and of iron and lead pipes, can be ascertained, without the 

 use of a balance of any kind, and even while these articles make a 

 component part of machinery. After an explanation of cohesion, 

 there is exhibited the comparative strength of materials to resist com- 

 pression, or being crushed, as the stifiiiiess of beams, bars, &l.c. longi- 

 tudinal strength to resist being pulled asunder in the direction of their 

 lengths ; as cables, chains and anchors, bars, Sic. ; also, power to 

 resist twisting or torsion, as gudgeons, journals of shafts, &ic. witli 

 rules for calculating the strength of the same, and of wheels, revolv- 

 ing shafts, and other parts of machinery. 



The next thirty pages treat of matter geometrically defined, and 

 contain rules and calculations for determining the solid contents and 

 superficies of walls, timber and other like substances of every form. 

 This is followed by numerous practical remarks on friction, and other 

 kinds of resistance to motion, with rules for estimating their amount 

 and influence upon various kinds of machinery. " From the resist- 

 ance of fiiction alone," it has been observed by Mr. Ferguson, 

 " there are few compound machines that do not require a third part 

 more power to work them when loaded, than is sufficient to constitute 



