Intelligence and Miscellaneous Articles. 395 



Thus 341*46 cal. were given off by the cylinder in cooling 19°*82 

 or 17*23, cal. for one degree. Of this 8*34 cal. are due to the 

 steel cylinder itself, leaviDg 8*89 cal. for 1O01 grams of liquid 

 ammonia or 0*888 per grain = specific heat. In a second and third 

 experiment the values 0*897 and 896 were obtaiued. The 

 determination of the specific heat of liquid ammonia would be 

 influenced, as stated, by the latent heat of condensation of part of 

 the small quantity of vapour present, when the cylinder cools in 

 the calorimeter. This would to a degree be neutralized by the 

 contraction of the liquid ammonia itself in the cooling and the 

 consequent formation of more vapour space. 



It seemed desirable to ascertain the influence of these factors 

 collectively by experiment. For this purpose specific heat deter- 

 minations were made in a way somewhat different from the 

 ordinary. The steel cylinder was cooled in an iron shell in melting 

 ice, instead of being heated, and then introduced into the warm 

 calorimeter water. The mode of precedure was in detail similar to 

 that described above, and we will therefore only give our results. 

 In three experiments the values 0*878, 0*863, and 0*892 were 

 obtained. They are a trifle lower in their average than the results 

 obtained by the ordinary method. It is reasonable to assume that 

 they are somewhat low, while as stated the other results are 

 presumably somewhat high ; and in order to arrive at the specific 

 heat of this substance nearest the true value from our experimental 

 evidence, we will take the average of our six values, viz. : 

 0*888 ) 0*878 ) 



0*897 [ 1st series, 0*863 I 2nd series, 



0*896 J 0*892 J 



and state it as being= 0*8857. 



"We beg herewith to acknowledge our obligations to Chancellor 

 W. S. Chaplin and Prof. Wm. B. Potter for kindly placing the 

 laboratories under their charges at our disposal. — Sillimans Journal, 

 March 1893. 



ON THE OFFICIAL TESTING OF THERMOMETERS. 

 BY H. F. WIEBE. 



In the year 1885 the Imperial Standards Commission undertook 

 on a large scale the official testing of thermometers which is of 

 such great importance both in science and in practice ; while pre- 

 viously only a few institutions, such as the Naval Office, had 

 occupied themselves to a limited extent with the investigation of 

 thermometers. These official testings were transferred to the 

 recently established Physical Technical Imperial Institute, to which 

 since then a great number of thermometers have every year been sent 

 for investigation. (In Ilmenau there is a branch for these testings.) 

 Through the great progress which has been made since Jena glass 

 has been used for thermometers, it has been possible to undertake 

 a permanent guarantee for the results obtained in such testing ; 

 and from the uniformity of this glass the thermometric constants, 

 once determined, may be universally adopted. The testing takes 



