proceedings: philosophical society 299 



h, and increases with increasing A. Applications of the results to calori- 

 metric problems in the laboratory as well as to many industrial prob- 

 lems were suggested. An approximate mathematical expression for the 

 results obtained was presented. 



By invitation Mr. L. H. Adams presented an illustrated paper on 

 The thermoelectric power of pure metals. Thermoelectric force and the 

 closely allied thermal and electrical effects have an important bearing 

 on many aspects of the behavior of metals and an extended knowledge 

 of these quantities would go far toward a solution of the problems of 

 metallic conduction. The results enable one to calculate 4 other quan- 



dE d 2 E 

 tities, viz. -77= , -7= , Peltier effect, and Thomson effect. The last named, 

 dr dl 2 



although extremely difficult to measure calorimetrically, can be deter- 

 mined by the electrical method with considerable accuracv. Curves 



dE 

 illustrating the course of -r=. and of the Thomson effect from absolute 



dr 



zero to very high temperatures show that the relations involved are 

 much more complicated than has hitherto been supposed, and explain 

 the difficulty of obtaining a suitable equation for representing the ther- 

 moelectric force as a function of the temperature. It is of interest to 

 note the extraordinary sensitiveness of the thermoelectric force to 

 slight impurities in the metal. 



The communication was discussed by Messrs. Swann, Burgess, and 

 White. The Chair expressed to the speaker the Society's thanks for 

 his very suggestive paper. 



Mr. A. Hall then spoke on The equatorial micrometers of the Naval 

 Observatory, illustrating his communication with lantern slides. The 

 micrometers constructed by Clark, Saegmiiller, Warner and Swasey, 

 and Repsold were compared. The last is a large instrument, made of 

 iron and steel, with a platinum-iridiuni position circle, purchased by 

 the Naval Observatory in 1913. An eye-piece microscope is provided 

 for the examination on the telescope of the micrometer screw. The 

 readings of the screw can be made in the usual manner or can be printed 

 on a Morse fillet, on two type-metal wheels which carry raised figures. 

 Great care is taken to have the illumination of the threads symmetrical, 

 and in every way provision is made to eliminate systematic errors. 



The Secretary read an invitation from the Washington Academy of 

 Sciences inviting members of the Society to attend a lecture by Dr. L. 

 H. Baekeland at the New National Museum on March 23 at 8.30 

 p.m. 



The 771st meeting was held on April 1, 1916, at the Cosmos Club; 

 President Brigg.s in the chair, 44 persons present. The minutes of the 

 770th meeting were read in abstract and approved. 



Mr. R. S. Woodward presented a communication on The extraction 

 of square roots of numbers. Referring to a previous communication to 

 the Society by the author on the same subject some further applica- 

 tions were explained of the formula 



