1872.] 187 [Jeffries. 
Dr. C. T. Jackson referred to the singular fact that deep 
mines in California are never affected by earthquake shocks. 
Dr. B. Joy Jeffries spoke of, and explained the usual 
methods of testing patients for color blindness and inter- 
ruptions of color perception in the visual field in disease. 
He also exhibited and explained a model of the instrument for 
testing color blindness, shown by Woinow at the last Heidelberg 
meeting of ophthalmologists. This consists of an apparatus with a 
rotating disk, whose centre is black and white, next outside a ring of 
red and green, next a ring of violet and red, next outside of violet 
and green. When rapidly rotated the centre appears of course gray, 
i. €., of black and white mixed. The outer ring will also appear gray 
to the red blind patient, as he can perceive gray from the two colors 
' presented, violet and green. The middle ring will appear gray to the 
green blind, since he can see gray by the mixture of violet and red. 
The inner ring will appear gray to the violet blind, as red and green 
give him gray. Color blindness is the loss of perception, in whole or 
part, of one or more of the three energies which we call red, green 
and violet. Since the experiments of Maxwell, Helmholz and other 
physiologists are agreed that these must be taken as the three base 
colors of light. Dr. Jeffries also spoke of some cases of congenital 
microphthalmos, where, although the globe was only minute, and the 
place of the cornea a slightly bluer shade than the sclerotic, yet the 
finest shades of color could be detected, whilst vision as to shape and 
form was very defective. 
Section of Entomology. May 22, 1872. 
Mr. B. P. Mann in the chair. Ten members present. 
Mr. Burgess read a letter from the Executor of the will of 
the late Wm. H. Dale,.announcing the bequest of his insect 
cabinet and the sum of five hundred dollars to the Section. 
Mr. Mann spoke of the activity of Bruchus granarius in 
the pupa state. The larva is yery injurious to the coffee- 
bean in South America. 
