Chemistry and Physics. 289 



larly the two strongest, viz., (1) the production of hydrocarbons 

 when hardened steel or white cast iron is dissolved in acids; and 

 (2) the reversed analogy of the copper and tin alloys in favor of 

 the physical theory. 



C. The Limit of the Liquid State of Matter; by J. B. 

 IIanxay. — The conditions under which an in\ < ■stigal ion is curried 

 "lit often predetermine the conclusions to he drawn from the ob- 

 servations made. That this 1ms been the case with the observa- 

 tions made upon the upper confines of the liquid state, there is 

 now ample evidence to show. When Cagniard de Latour, on 

 heating liquids in sealed tubes, noticed the disappearance of the 

 liquid surface, he came to th< c i 1 isi ji tl it the liquid state had 

 ceased to be possible, and that the substance had passed into the 

 gaseous state. But Latour had no means of varying the volume 

 of his liquid to observe whether or not increase of pressure 

 might again induce liquefaction. This defect was removed by 

 Dr. Andrews, who constructed the well-known apparatus for 

 varying the volume by means of a screw; and it is to the work 

 performed with this apparatus that the above remark is applied. 

 By two modes of observation Dr. Andrews arrived at the con- 

 elusion that the liquid and gaseous states of matter were con- 

 tinuous. The experiments being conducted in transparent glass 

 tubes, the appearance of the contained fluid constituted one 

 "lode, and the registration of the pressure constituted the other. 

 X'H/nr ,./' //,,.sv methods r,,,ihJ A// the n> <-> s«iti> s «;/' the case give 

 «»y aid' in deternei ',,'nuj the shite of matter. \ >r. Andrews's 

 method of demonstrating the continuity, by passing from a 

 lower to a higher temperature under a pressure which prevented 

 the formation of vapor, ensured the homogeneity of the fluid 

 under examination, and precluded the existence of a visible 

 liquid surface : and as liquid and gas are equally transparent, no 

 tidings of the state of the fluid under examination could come to 

 him by observations of its appearance. How did Dr. Andrews 

 tell when his tubes contained liquid '! By lowering the pressure 

 till a meniscus was seen. Then, the formation of a menisens is 

 th< nnh/t.sf of tin I 'inn hi state. Dr. Andrews then obliterated 



pressure, and raised the temperature till on again re, hieing the 



aused by the thermal velocity of the mol 

 imber of them in a space, the change shoi 



stic property of the liquid state is then tl 



,n sufficient to form a surface, or simply s 

 Id this propertv be retained in a visible f 



