104 Analysis of Scieyitific Books, 



throw much new light upon the nature of the compounds of 

 carbon and hydrogen, respecting which very much remains yet to 

 be ascertained. 



A Comparison of Barometrical Measurement with the Trigonometri' 

 ca I Determination of a Height at Spiizbergenf by Captain Edward 

 Sabine, F.R.S. 



Op this paper we have already given an abstract,* and also of 

 the following one, containing Experimental Inquiries relative to 

 the distribution and changes of the Magnetic Intensity in ships of 

 wary by George Harvey, Esq.t 



Experiments on the Elasticity and Strength of hard and soft Steelt 

 by Mr. Thomas Tredgold. 



Ira piece of very hard steel be softened, it is natural to suppose 

 that the operation will produce a corresponding change in the 

 elastic power, and that the same load would produce a greater 

 flexure in the soft state than in the hard one, when all other 

 circumstances were the same, Mr. Coulomb inferred from some 

 comparative experiments on small specimens, that the state of 

 temper does not alter the elastic force of steel ; and Dr. Young's 

 Experiments on Vibration led to the same conclusion (Nat. 

 Philos. II. 403). But the subject appeared to require further 

 investigation, and particularly because it afforded an opportunity 

 of ascertaining some other facts respecting steel, which had not 

 been before examined. 



In making the experiments described in this paper, each bar 

 was supported at its ends by two blocks of cast iron. These 

 blocks rested upon a strong wooden frame. The scale to contain 

 the weights was suspended from the middle of the length of the 

 bar, by a cylindrical steel pin of about three-eighths of an inch in 

 diameter. And as in experiments of this kind it is desirable 

 to have the means of raising the weight from the bar, without 

 altering its position, in order to know when the load is sufficient 

 to produce a permanent change of structure, a powerful screw 

 with a fine thread was fixed over the centre of the apparatus, by 

 which the scale could be raised or lowered, when the cords on 

 which the screw acted were looped on to the cross pin by which 

 the scale was suspended. 



To measure- the flexure, a quadrantal piece of mahogany was 

 fixed to the wooden frame ; two guides were fixed on one edge of 

 the mahogany, in which a s^ertical bar slided, and gave motion 

 to an index. The bar and index were so balanced, that one 



• Vol. XVII. p. 268. t Ibid. p. 26J. 



