298 proceedings: philosophical society 



large part of the country is suitable for cultivation but because of the 

 distance from market the raising of cattle and sheep is the industry 

 most developed. The vegetation is remarkable, particularly the tree 

 ferns, which grow to great size. The native Maori people are much 

 like the Hawaiians in character and language and are of a very high 

 order of intelligence. Australia is quite unlike New Zealand in its physi- 

 cal features. The interior is a great plain and is generally quite arid 

 as the outside fringe of mountains on all sides prevents the rains from 

 reaching it. The presence of copious deep level water makes possible 

 the use of artesian wells and much of the interior may be developed 

 by irrigation. The interesting question as to the source of this deep 

 level water was discussed briefly. The flora and fauna are peculiar. 

 The aborigines are entirely unlike those of New Zealand, being of negroid 

 type and of a very low state of culture. The address was illustrated 

 by wall maps and lantern slides. 



To express the appreciation of the meeting for the delightful and 

 instructive address, the President called for a rising vote, which was 

 unanimous. 



The 722cl meeting was held on March 15, 1913, at the Cosmos Club. 

 Vice-President Fischer in the chair; 27 persons present. The minutes 

 of the 719, 720, and 721st meetings were read and approved. 



Because of illness, Mr. G. W. Spencer, who was to have presented a 

 paper Relationship between terrestrial gravity and observed Earth move- 

 ments of eastern America, was unable to address the meeting. 



Mr, I. G. Priest read a paper on A photometric error sometimes accom- 

 panyifig the use of a pair of nicols, and a proposal for its elimination, 

 illustrated with lantern slides. In extensive optical trains such as occur 

 in spectrophotometers and colorimeters the use of a pair of nicols fol- 

 lowing the simple theory may be impaired by oblique reflection^ of the 

 plane polarized beam whose plane of polarization is rotated with the 

 rotating nicol. An example was cited and illustrated by lantern slides 

 and formula given showing variation of intensity of beam from propor- 

 tionality to the square of the sine of the angle 6 thru Avhich analyzing 

 nicol is rotated from the position of " crossed nicols." A triplet of nicols 

 in train instead of a pair is proposed with end nicols fixed and middle 

 one rotating, in which case, with principal planes of end nicols parallel, 

 the intensity is proportional to sin^ d, and if perpendicular, to sin^ d cos^ 0. 

 Trouble may be more simply eliminated by using only a pair of nicols 

 but rotating the polarizer instead of the analyzer, provided the beam 

 incident on polarizer is entirely unpolarized. The paper was discussed 

 by Messrs. Coblentz and Tillyer. 



Under informal communications Mr. W. Bowie presented a paper on 

 The precise level net of the United States, giving the results of the recent 

 adjustment by the Coast and Geodetic Survey of the different circuits 

 of the precise leveling net of the United States. 44,720 kilometers of 

 leveling have been run in two directions and about 10,700 permanent 

 bench marks have been placed in all but seven states. The values 



