208 Notices respecting Ncjo Booh. 



The use of iron for beams has been lately much and deservedly re- 

 sorted to. In the application of a new material it is to be expected 

 that there will be occasional failures, partly owing to motives of (Eco- 

 nomy, and partly to want of skill in the builder. The price of iron 

 renders it desirable that the smallest quantity should be used which is 

 consistent with safety and durability. 



There are several popular treatises on the strength of iron and the 

 form of beams ; but the rules contained in them are frequently at va- 

 riance with experiments, and therefore mislead the practical man, who 

 has not leisure or ability to investigate the principles upon which they 

 are founded. 



In this tract, the author investigates the theory of strength, and of 

 resistance to fracture and deflection, and supplies by judicious experi- 

 ments the defective elementary data, giving the particulars at large 

 of numerous experiments on iron of various forms and dimensions, 

 so as to enable a practical builder to satisfy his own mind of the 

 ground upon which the deductions are made. These experiments 

 prove that the form recommended by the late Mr. Tredgold is in- 

 ferior to others which have since been adopted, and also that the for- 

 mula given by Mr. Tredgold for determining the strength is incorrect, 

 and may lead to serious errors*. 



Much of the work is occupied by the subject of the transverse strength 

 and strain, and some useful deductions are made on the ultimate de- 

 flection, — a point which at present deserves further investigation. 



The author acknowledges his obligations to Messrs. Fairbairn and 

 Lillie for the assistance they rendered him at their foundry, by which 

 he was enabled to adopt a scale of dimensions seldom within the 

 means of a theoretical investigator. Instances of liberality of this kind 

 are frequently met with in this country, much to the honour of the 

 persons who thus manifest themselves friends to their country and to 

 science. 



The result of Mr. Hodgkinson's experiments on cast iron beams hav- 

 ing the bottom rib containing more than half the matter of the whole 

 beam, shows that the breaking weight was proportionate to the area 

 of the bottom rib, and to the full depth of the beam, and inversely as 

 the length, subject to a constant factor depending on the position of 

 the beam in the casting, the vertical castings being about -jVth stronger 

 than the horizontal castings ; the quality of the metal will also modify 

 the factor in some degree. In such important experiments as these, 

 the determination and statement of the specific gravity and hardness, 

 together with the modulus of elasticity of the material, would add to 

 their value, with very little additional burden to the operator. 



On the Economy of Machinery and Manufactures. By Charles Bab- 

 BAGE, Esq. A.M., Lucasian Professor of Mathematics in the Univer- 

 sity of Cambridge, and Member of several Academies. London, 1 832. 

 Although the present volume does not properly come within the 



sphere of a scientific Journal, yet the principles which it discusses 



♦ Analyses of the first and second editions of Mr. Tredgold's Essay on 

 the Strength of Cast Iron, will be found in Phil. Mag. vol. Ix. p. 137; and 

 vol. Ixiii. p. 52. 



