294 
OBITUARY NOTICES. 
telescope; the flexure of the 6-inch transit circle and the 
5-inch alt-azimuth instrument was reduced to a minimum 
by using for the tubes and axes single pieces of steel machined 
on the inside and the outside. In 1875 he devised instru¬ 
ments for measuring accurately the relative positions of 
Venus and the Sun as shown on the photographs taken dur¬ 
ing the transit of Venus, December 9, 1874. He invented 
the spherometer caliper in 1877, which is the most accurate 
instrument known for determining the figure of the pivots 
of astronomical instruments. He made extensive experi¬ 
ments in photography with the view of determining the best 
reagents and form of apparatus for photographing the solar 
corona. 
He took part in numerous expeditions for scientific and 
astronomical observations. In 1865-1866, on the U. S. 
monitor Monadnock, he studied the effect of the iron armor 
in modifying the magnetic indications of the compass, and 
determined the magnetic elements at many ports in a cruise 
from Philadelphia around South America to San Francisco. 
The Smithsonian Institution published the report on this 
magnetic work in 1871 in a quarto volume of 225 pages. 
He observed the total eclipse of the sun, August 7, 1869, at 
Des Moines, Iowa, and there discovered the coronal line 
K 1474; the total solar eclipse of December 22, 1870, at 
Syracuse, Sicily; the transit of Venus at Hobart, Tasmania, 
on December 9, 1874; the transit of Mercury at Austin, 
Texas, May 6, 1878; the total solar eclipse at Creston, Wy¬ 
oming, July 29, 1878; the transit of Venus at Washington, 
D. C., December 6,1882. He was appointed a member of the 
U. S. Transit of Venus Commission in 1871; served on this 
commission in devising apparatus and fitting out the United 
States expeditions for the transits of 1874 and 1882 ; was 
assigned to duty in 1875 for reducing the observations made 
by these parties; measured the photographic plates with new 
apparatus ; published a paper in 1882 on the “ Relative ac¬ 
curacy of different methods of determining the solar par¬ 
allax,” defending the continued use of photography; and 
