618 Intelligence and Miscellaneous Articles. 



in the seventh Report of the British Association (i. e. that for 

 1837). The need spoken of by G-auss for accurate determinations 

 of the magnetic declination, horizontal intensity, and dip, taken at 

 stations uniformly distributed as in a network over the surface of 

 the earth, is eveu now very imperfectly supplied, particularly in 

 the southern hemisphere ; still much has been done in the last 

 fifty years, and we were glad lately to notice that observations of 

 that kind are being carried on by Dr. Doberck at Hongkong. Prof. 

 J. 0. Adams's work here set forth forms an important and valuable 

 contribution to the progress of knowledge iu this department ; 

 aud the tables contained in it, after being most carefully calculated 

 by the assistants at the observatory, have also been verified by 

 some of those on the staff of the 'Nautical Almanac' Altogether 

 these two volumes will form an enduring monument to the memory 

 of one scarcely known to the general public except as a discoverer 

 of Neptune by the great achievement of calculating its path before 

 it was actually seen, in which he had the priority. 



LXI. Intelligence and Miscellaneous Articles. 



NEW EESEAECHES INTO POUILLET's PHENOMENON (THE HEAT 

 DEVELOPED IN WETTING POWDERS). BY TITO MARTINL 



"IN this third memoir, published in the ' Proceedings of the Royal 

 -*- Institute of Venice'*, I have demonstrated, by means of 

 numerous experiments, that there are powders (thermometer-glass, 

 quartz, calcium carbonate, &c.) which moisten well with water or 

 other liquids, but which heat little or not at all however finely 

 reduced. Other powders, like silica, the silicates,- vegetable earth, 

 artificial coals, undergo a great rise in temperature whether bathed 

 in water, alcohol, ether, &c. 



With silica and animal charcoal I made new calori metric mea- 

 sures, and obtained values larger than those recorded in my 

 previous paper f, because I was careful to dry the powder well. 

 The new values- which represent the heat yielded- to the calorimeter 

 vary from 17 to 18'50 calories about, according to the degree 

 of dryness of the powder. 



It is my opinion that a degree of heat so considerable is pro- 

 duced by the modification that the liquid undergoes when absorbed 

 by the powder, by means of which modification the liquid is 

 reduced to a condition of lower molecular energy. As a matter of 

 fact, putting a determined weight of powder into a constant calori- 

 nietric mass, 1 have been able to observe a diminution in the mass 

 of the calorimeter, because the specific heat of a part of the water 

 absorbed becomes equal to that of the ice. The demonstration of 

 this interesting result is founded upon the following experiment. 



* Atti del Reale Istituto Veneto, T. l ; x. parte seconda, p. 615. 

 t Philosophical Magazine, March 1899, p. 329. 



