60 Proceedings of Societies, [ January, 
PROCEEDINGS OF SOCIETIES. 
PHILOSOPHICAL Society or Wasuineron, November 20, 1875. 
— Dr. Woodward, of the Army Medical Museum, gave an account, illus- 
trated by photographs and illuminated photographic pictures thrown 
upon a screen, of spurious lines, noted by Dippel, and more lately in a 
British periodical, as genuine, seen on certain diatoms. The species 
Frustularia Saxonica has transverse lines of extreme fineness, and lon- 
gitudinal lines had been described by Dippel and others, some assert- 
ing that the latter were coarser and others that they were finer than 
the transverse ones. Dr. Woodward showed very clearly by his illumi- 
nated slides, enlarged on the screen forty-five thousand diameters, that 
the longitudinal lines appeared not only on the diatom but also on the 
Space external to it, and similar lines appeared about specks of dirt on 
the plate. These could be varied in coarseness by different illumina- 
tions of the object. Hence he concluded that they were spurious, and 
caused by diffraction of light from the midriff, or the edge of the diatom, 
lines could be determined by the fact that they did not vary in number 
under varying illuminations or focusing; they were either seen uni- 
formly, or not seen at all. 
December 4, 1875. Professor Henry read a short account of some 
peculiarities of partial loss of vision in circumscribéd portions of the 
retina, which Dr. Woodward explained by a congestion of one, or a 
part of one, of the tubercule quadrigemine of the optic nerves. 
formation was always the result of motion, either of air or water. Major 
Powell contended for the formation of ripple marks at the bottom of 
at motion capable of producing ripple marks might be propagated even 
to the depth of over one hundred fathoms. 
AMERICAN ACADEMY or ARTS AND SCIENCES, Boston, November 9: 
— Mr. Sereno Watson presented a paper on a collection of plants re- 
cently made by Dr. E. Palmer, in Guadalupe Island, off Lower Cali- 
fornia. It was found to contain one hundred and nineteen species, in- 
