proceedings: philosophical society 23 



vapor; in the first case the specific heat is determined and in the sec- 

 ond the latent heat of vaporization, when proper corrections are 

 made. The unique features of this instrument are: 



1. Central location of the heater and thermometer. 



2. Distribution of metal connections between calorimeter and 

 jacket to minimize errors from lead conduction. 



3. Provision of a device for rapid cooling of the calorimeter. This 

 consists of a copper ring which can be moved within the jacket so as 

 to short-circuit thermally the insulating air space and permit the 

 escape of heat to the cooled jacket. 



4. Surface temperature equalizer for rendering the annulment of 

 thermal leakage independent of thermal irregularities in the interior 

 of the calorimeter. Measurements were made in the range of tem- 

 perature from — 40°C. to + 40°C. of (a) the specific heat of liquid 

 ammonia by two methods, one under saturation conditions, the other at 

 constant pressure; (b) the latent heat of vaporization of ammonia; and 

 (c) the latent heat of compression of liquid ammonia. 



Discussion. Mr. White thought the aneroid calorimeter a great 

 advance in calorimetry. He discussed also the relative advantages of 

 large and small calorimeters; a small instrument is to be preferred, 

 provided proper care be used in the details of construction. Mr. 

 Swann spoke of some experiences indicating the advantage of the 

 aneroid type of instrument over the stirred-liquid type. 



Informal communications. Mr. M. D. Hersey presented as an in- 

 formal communication a list of theorems relative to the errors of phy- 

 sical measurements, which he has gradually developed during the 

 past six years as a by-product of other work. There are five theo- 

 rems relating to apparatus, two to observations, and seven to com- 

 putations. The manuscript notes, such as they are, are available to 

 any individual interested. Fragments of this work already published 

 are to be found in the Journ. Wash. Acad. Sci., 1: 187, 1911; 3:296, 

 1913; 6:620, 1916; and in the B. A. Rep., Birmingham, 399, 1913. 



Mr. White spoke informally on the swelling and splitting, because 

 of amalgamation by mercury, of the platinum element of a thermostat 

 that had been stored away for two or three years. Mr. Wenner 

 remarked that he had many times noted similar effects. 



Mr. Humphreys read a humorous poem giving a soldier's opinion 

 of the climate of the Rio Grande. 



The 46th annual meeting (780 th regular meeting) was held on De- 

 cember 9, 1916 in the assembly hall of the Cosmos Club. President 

 Briggs and President-elect Buckingham in the chair; 34 persons 

 present. The minutes of the 45th annual meeting were read. 



The report of the Secretaries was read by Mr. Agnew. Three 

 members, viz., Messrs. Cleveland Abbe, Henry H. Bates, and 

 F. B. McGuire, died during the year; 14 new members were elected; 

 8 members were transferred to the absent list; 2 members resigned; 

 and 1 member was dropped. The present active membership is 149. 



