60 BULLETIN OF THE 



sextiles of fil days, in leap years; the last month, or sextile, in 

 common years to have one day less. He explained and illus- 

 trated by examples the transition from the present system. 



Mr. Coffin suggested that this transition would be simplified 

 by beginning the year one day earlier than at present. 



Mr. J. J. Woodward made a communication on 



DIFFRACTION PHENOMENA IN THE FIELD OP THE MICROSCOPE : 



illustrating by photographs of Frustulia Saxonica thrown upon 

 a screen, and showing that spurious stria3 may be produced by 

 throwing the light obliquely on the object. 



( The paper is published in the Monthly Microscopical Journal, December, 

 1875, p. 274.) 



The President read, as his Annual Address, 



AN ACCOUNT OF RESEARCHES ON SOUND IN ITS APPLICATION TO 

 FOG-SIGNALS. 



{This forms part of the Report of the U S. Light House Board for 1875.) 



96th Meeting. December 4, 1875. 



The President in the Chair. 



Thirty-five members and visitors present. 



The election of Commander E. P. Lull, U. S, N., as a mem- 

 ber of the Society was announced. 



Mr. Joseph Henry read a paper on 



half-vision : 



describing the phenomena in his own case, and illustrating by a 

 diagram the luminous circle and colored spectra presented to his 

 vision. 



Mr. Woodward followed with remarks on the frequent ob- 

 servance of half-vision, and the amount of literature on the 

 subject ; describing an injury to his own eyes from the use of the 



