358 
PHILOSOPHICAL SOCIETY OE WASHINGTON. 
Mr. E. D. Preston presented a paper, with lantern illustra¬ 
tions, on Hawaii,—an unscientific account of a scientific expedi¬ 
tion. [Published in Science, vol. xi, pp. 841, 894.] 
Mr. R. A. Harris presented A new way of indicating the 
acceleration of a point referred to polar coordinates. [Hot pub¬ 
lished.] 
519th Meeting. May 12, 1900. 
President Sternberg in the chair. 
Thirty-three persons present. 
Mr. J. E. Watkins read A chapter in the early history of 
marine propulsion, illustrating it by lantern slides. [Not pub¬ 
lished.] 
Mr. G. W. Littlepiales presented a paper on Marine screw 
propulsion, outlining the general features of the theoretical side 
of the subject. [Not published.] 
Mr. R. A. Harris described Some experiments in wave motion, 
stating the underlying theoretical considerations, and giving the 
results of observations on stationary waves in enclosed areas of 
various shapes. [Not published.] 
The thanks of the Society were extended to Mr. Taylor, Naval 
Constructor, for his invitation to the members of the Society to 
witness an interesting exhibit of the work of the experimental 
model-basin at the Navy Yard this afternoon. 
520th Meeting. May 26, 1900. 
President Sternberg in the chair. 
Seventeen persons present. 
Mr. F. W. True read a biographical notice of Mr. D. W. 
Prentiss. [Not published.] 
Mr. H. C. Bolton presented by invitation a paper on An ex¬ 
perimental study of radio-active substances. Photographs taken 
by the aid of such bodies were exhibited and the room being 
darkened, specimens of the substances, were passed around. 
