138 Notices respecting New Books. 



never be strained in constructions of any kind whatever. Ne- 

 vertheless it would be extremely desirable that some accurate 

 experiments on the extension of boches should be made, when 

 the strain exceeds the elastic force ; as by that means some- 

 thing important regarding the ductility of matter might be 

 discovered ; and perhaps they might throw some light on the 

 nature and arrangement of the ultimate particles of bodies. 



In the sixth section he has shown how to obtain some of 

 the most useful practical rules from the first principles that 

 are furnished by experience. He has conducted the investiga- 

 tion of these rules in a manner somewhat different from other 

 writers, and has avoided the use of fluxions. Several new 

 cases are investigated, mid some addition is made to the 

 theory of resistance ; the reader will find examples of this in 

 treatmg of the strength of beams, art. 77 to 85 ; the deflexion 

 of beams, art. 90 to 93 ; the strain upon beams, art. 96 to 

 104; the resistance to torsion, ait. 222 to 227; and the re- 

 sistance of columns, art. 230 to 246. 



In the seventh section he has considered the resistance of 

 beams to impulsive force. In this section will be found many 

 important rules, with examples of their application to the 

 moving parts of engines, bridges, &c. ; wherein the advantage 

 gained by employing beams of the figures of equal resistance 

 is shown. 



The seventh section is followed by an extensive Table of 

 the Properties of Materials, and other Data, often used in Cal- 

 culations, arranged alphabetically. By means of this table 

 the various rules for the strength of cast-iron, contained in the 

 work, may be applied to several other kinds of materials. 



A note, which the author has added at the end of the table, 

 on the chemical action of some bodies on cast-iron, will be 

 read with interest by those who employ cast-iron where it is 

 exposed to the action of sea-water. 



Each plate is accompanied by a page of descriptive letter- 

 press opposite to it, with references to the articles which the 

 figures are intend(,d to explain. 



And, in general, it will be found that the examples are se- 

 lected with a view to explain the practical application of the 

 rules ; and to make the reader aware of the limits and pre- 

 cautions to be attended to. In fact, the want of such informa- 

 tion has often brought theory into discredit with some men, 

 whereas the fault ought to have fallen on the person that mis- 

 applied it. 



In a note, the author acknowledges himself greatly indebted 

 to Dr. T. Young for showing the necessity of attending to the 

 strain which produces permanent alteration on the materials 

 employed. — Nat. Phil. vol. i. p. 141. In 



