234 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



portant fact that the specific heat of water, hitherto supposed 

 to be greater than that of any known substance except hy- 

 drogen, is really less than that of a mixture of water with 

 methyl alcohol, in various proportions. This mixture, there- 

 fore, lias a specific heat next to hydrogen. 



Dahlander has communicated to the Swedish Academy of 

 Sciences the results of his observations on the comparative 

 rapidity with which heated solid bodies are cooled by im- 

 mersion in various liquids. If the cooling power of water 

 be taken as unity, that of alcohol is 0.58 ; of mercury, 2.07; 

 of a concentrated solution of salt, 1.05 ; and of a concentrat- 

 ed solution of copper sulphate, 1.03. The rapidity of cooling 

 increases with the increased temperature of the liquid. 



Ditte lias proposed to show the heat produced by chem- 

 ical action, by adding 125 grams of water to 100 of boric 

 acid. The heat produced is so great that an ingot of Par- 

 cels fusible metal put into the mixture is completely fused 

 in a few seconds. 



Olivier has observed the curious phenomenon that if one 

 end of a bar of steel fifteen millimeters square and seventy 

 to eighty centimeters long be held against a revolving grind- 

 stone, one hand grasping the bar at its middle point, the oth- 

 er at the end, the middle portion remains quite cold, while 

 the end farthest from the stone becomes too hot to touch. 

 This appears to indicate the transference of energy along the 

 bar in some other form than as heat. 



Joule has made a new set of experiments with a view to 

 increase the accuracy of his former determinations of the 

 mechanical equivalent of heat. The result he has now ar- 

 rived at, from the thermal effects of the friction of water, is, 

 that taking the unit of heat as that which can raise a pound 

 of water weisrbed in vacuo from 60 to 61 of the mercurial 

 thermometer, its mechanical equivalent, reduced to the sea- 

 level at the latitude of Greenwich, is 772.55 foot-pounds. 



Aitken has described an apparatus for illustrating the con- 

 version of the motion of heat possessed by matter at its nor- 

 mal temperature into work, in which he anticipated Preston's 

 experiment. Two glass tubes entered a large bottle through 

 its cork, one passing to the bottom, its upper end being 

 drawn out to a fine jet. The other terminated just below 

 the cork, where were attached some strips of blotting-paper. 



