48 PEOCEEDINGS: PHILOSOPHICAL SOCIETY 



The 714th meeting was held on November 9, 1912. The following 

 papers were read: 



Media of high refraction for use with the microscope: H. E. Merwin, 

 of the Geophysical Laboratory. The chief purpose of the results de- 

 scribed was to make possible the identification of minerals. The micro- 

 scope can be used for determination of refractive index of all solutions 

 that are not opaque. A refractive index chart was exhibited covering 

 a range of 1.5 to 3.0, and the physical properties of the mixture used to 

 get this range were described. This range of media can be made 

 standard by weighing out the materials. The absorption and heat 

 effects were spoken of, and the variations of some of the media were 

 described. 



The last meeting of the International Geodetic Conference at Hamburg: 

 0. H. TiTTMANN, of the Coast and Geodetic Survey. A brief account 

 was given of the origin and growth of what is now the International 

 Geodetic Association, and of its present organization and its work, this 

 being followed by a brief outline of what the Hamburg meeting dealt 

 with. The mode of government of the State of Hamburg was men- 

 tioned. About 50 delegates attended the conference from the 20 dif- 

 ferent countries represented. Much interest was taken in the reports 

 on the variation of latitude work, and the next most important question 

 was triangulation, of which the United States has generally reported 

 the most work done. Isostasy was not much discussed. The social 

 functions and points of interest visited were spoken of. 



Under Informal communications Mr. Tittmann spoke of an automo- 

 bile without springs, invented by Josef Hofmann, the pianist, and Mr. 

 Bowie called attention to the completion of the marking of the boundary 

 between Alaska and Canada north of the Yukon River, under the direc- 

 tion of Mr. Tittmann as commissioner on the part of the United States. 



Before closing the meeting the chair announced the. death of Dr. 

 Robert Fletcher a past president of the Society. 



The 715th meeting, held on November 23, 1912, was devoted to a 

 general discussion of The application of the microscope to physical prob- 

 lems, the opening paper being given by Mr. F. E. Wright. 



In introducing the subject the speaker grouped the uses of the micro- 

 scope under three principal heads, (1) Qualitative, as a magnifying 

 glass, a seeing instrument; (2) as a measuring device, and (3) as an 

 optical instrument, such as for measuring the optical properties of min- 

 erals. Types of microscopes were exhibited and their construction and 

 manipulation described, illustrating the above mentioned uses of micro- 

 scopes. A number of accessories were also spoken of which are designed 

 to facilitate and extend the use of the microscope, especially as a meas- 

 uring and optical instrument. In the discussion which followed: 



Mr. Briggs spoke of his experience with the ultra-violet microscope, 

 pointing out its advantages and disadvantages, and the methods em- 

 ployed to overcome the disadvantages, such as finding the object to be 

 seen after it is on the stage, in which resort was had to the use of a 



