proceedings: philosophical society' 299 



resulting from the adjustment will probably be held as standard eleva- 

 tions for an indefinite time and be of great benefit to surveyors and 

 engineers. New circuits will be fitted to the old levelings as, while they 

 would theoretically give new and better values, the changes would be 

 small as regards practical use. The paper was discussed by Messrs. C. 

 A. Briggs, Rines, Wright, Humphreys, and Sosman. 



Mr. W. J. Humphreys presented an illustrated paper on Factors in 

 climatic changes in the past. The suggestion that the important factor 

 has been the presence of veils of volcanic dust in the atmosphere was 

 made in a revised form. Considerations of the material, density, and 

 size of particles of volcanic dust show that interference with ingoing 

 radiation would be five or more times that on outgoing radiation, which 

 would mean lower temperature. Calculations show that one-tenth 

 cubic mile of dust would account for a glacial period. 



The 723d meeting was held on March 29, 1913, at the Cosmos Club. 

 President Abbot in the chair; about 40 persons present. The minutes 

 of the 722d meeting were read and approved. 



Mr. L. W. Austin presented a paper on Recent experiments in radio- 

 telegraphy. Owing to non-receipt of data from S.S. Salem giving results 

 of tests between the Arlington station and the Salem while en route to 

 and from Gibraltar the speaker could not report on this work as he had 

 expected. The results of the United States Navy experiments of 19D9- 

 10 were reviewed and formulae discussed. The high power station at 

 Arlington was brieflj^ described. In it are incorporated the suggestions 

 and ideas developed in the 1909-10 work. It differs from most high 

 power stations in that it has a three tower arrangement for antennae 

 instead of the more usual umbrella type; one tower is 600 feet and the 

 other two each 450 feet high. Ground resistance has been practically 

 eliminated by grounding with copper net — this was found to be essential 

 and makes no difference in the radiant energy. The seasonal variation 

 of received signals was discussed — the energy received dropping during 

 the summer. Difference in ease of transmission during day and night 

 was pointed out; day conditions are generally more constant while at 

 night there are great fluctuations. Discussed by Mr. Bauer as to greater 

 ease of transmission along magnetic meridians; by Mr. Abbot as to 

 magnitude of difference between day and night conditions; by Messrs. 

 White, Humphreys, and Wolff as to the calculations at Arlington. 



Mr. F. A. Kolster spoke on National and international regulation of 

 radiocommunication. The uses and chief purposes of radiocommunication 

 are protection to life at sea, aid to navigation, communication between 

 ship and ship and shore, and naval and military operations. The first 

 regulation conference held in 1906 in Berlin was due largely to attempts 

 made to monopolize the business and the great amount of interference 

 due to amateurs. .At the second conference held in 1912, in London the 

 discussion w^as practically confined to matters relating to operation of 

 apparatus. Interference can l^e best avoided by restricting use of waves of 

 definite lengths for definite purposes, e.g.. wave lengths between 600 and 



