in Dr. Rees's New Cydopecdia. 425" 



ters are not calculated to encourage an English author to ven- 

 ture on the subject. 



Were we in possession of a correct and simple theory, — and the 

 tiling is not impossible, tiiough Eiilei and Lagrange have failed 

 in their attempts, — it miiiht be npjjjied to practice without any 

 other e.xperimental knowledge than th.at to be derived from ex- 

 periments made on beams or burs laid horizontally. Neverthe- 

 less, it would have been interesting to have had the tables of 

 Girard in English weights and measures, which certainly ought 

 to have been, done, as in its present state it is nearly useless to 

 the English reader. The manner of giving Buffon's experi- 

 ments is still less excusable, because they would have been better 

 in their original foim than as they are. 



The experiments on the strength of stones, which are taken 

 from the Encyclo. Brilaniiica, were published by M. Gauthey, 

 in 177-1, in Rozier's Journal de Pliysique, and were made in 

 conseejiience of a Memoir which M. Patte published in 1770, in 

 which he expressed his doubts respecting the stability of the 

 pillars Vi'hich support the dome of the French Pantheon. The 

 celebrated Soufflot, having heard of these experiments, con- 

 structed a machine similar to that used by Gauthey, and Perro- 

 net made a .third ; but it was ])erceivrd, in the course of their 

 experiments, that the friction and ch.ange of position of the 

 lever were so considerable as to influence the results. To re- 

 medy these defects a new machine was invented by M. Rondelet, 

 with which numerous experiments have been made. These are 

 published in his Trailc de I' Art de Batir, tome iii. p. SI, to- 

 gether with a description of the machine. It is to be regretted 

 that the direct cohesion of the stones crushed by this machine 

 has not been ascertained. — But to return to the author of the 

 article: He says, " We are aware that in different materials a 

 dififerent law may l)e observed between the strength of direct 

 cohesion and the resistance of the same body to a transverse 

 strain." It would be desiraijle to have some further particulars 

 if this really be the fact, but I should rather suspect the writer 

 to be mistaken. 



The third division is " on the transverse strain and strength of 

 beams." ivic. The theories of (ialileo and Leibnitz present such 

 erroneous results wlien applied to any other than rectangular 

 beams, that it is surprising, where a want of space is more than 

 once gomplained of, so nmch should be occupied in discussing 

 them, to the exclusion of other valuable matter; — for instance, the 

 resistance to twisting, and also what Dr. YounjJ call- resilience 

 and detrusion, might Imve been introduced. In the acco\mt of 

 the experiments of Du Ilamet there is u iliistake, \<hich also oc- 

 E e 2 eurs 



