C. A. Young—The Solar Eelipse. 233 
of them succeeded during totality. Professor Brackett, assisted 
by his wife, took this double instrument as his special charge, 
though he besides had the entire management. and oversight of 
all the photographic work; and not only so, but nearly every- 
thing that was ingenious in contrivance and skillful in execu- 
tion was his also. 
For photographing the corona, we had a six-inch telescope 
by Clark, with an object glass specially corrected for the actinic 
rays, loaned us by Professor Pickering. This was mounted 
upon an equatorial stand with clockwork, lent to us by Rutgers 
College. Mr. G. H. Calley was put in charge of this instrument 
and obtained with it three fine pictures of the corona with ex- 
posures of ten, fifteen and twenty-five seconds respectively. A 
plate which was to have had forty seconds exposure was un- 
fortunately lost. 
nly one instrument remains to be mentioned, that with 
which we attempted to explore the infra-red portion of the 
‘Spectrum. It was a spectroscope, with thermoscopic apparatus 
substituted for the retina. A tube about five feet long carried 
at the upper end a slit. two inches long taken from a Duboscq 
electric lantern. At the lower end of the tube was mounted 
a large spectrum-metal diffraction grating 5760 lines to the 
inch, in such a manner that it could be slightly turned by 
moving a long lever. In front of the grating was fixed a two- 
Inch quartz lens, at the end of a bifurcated tube, suitably dia- 
phragmed, and carrying at the other end a delicate line ther- 
mopile and a tasimeter. The whole apparatus was attached to 
a board equatorially mounted. In a large box close at hand 
was placed a delicate differential reflecting galvanometer, con- 
structed by Professor Brackett specially for the purpose—as, 
Indeed, was also the thermopile—both galvanometer and ther- 
aa distinctly superior to anything we could otherwise 
obtain 
_We had relied mainly upon the tasimeter, which Mr. Edison 
himself constructed, and gave to us, with a wholehearted gen- 
erosity which deserves and has our sincerest thanks. We 
received the instrument, however, only the day before leaving 
home, and when we came to experiment in the field we found 
It quite impossible to do anything with it without completely 
remodelling the whole apparatus, which there was no time to 
do. Whenever the direction of the instrument was changed to 
keep the collimeter pointed to the sun, the whole adjustment of 
the tasimeter was destroyed. It needs to stand unmoved upon 
a firm foundation, while the rays under investigation are 
brought to it by reflection. Under the circumstances we were, 
therefore, obliged to rely wholly upon the thermopile. 
Mr. A. D. Anderson managed the lever which moved the 
