228 Hi. Draper—The Solar Eclipse. 
corona, viz: it shines by light reflected from the sun by a cloud 
of meteors surrounding that luminary, and that on former 
occasions it has been infiltrated with materials thrown up from 
the chromosphere, notably with the 1474 matter and hydrogen. 
As the chromosphere is now quiescent this infiltration has taken 
place to a scarcely perceptible degree recently. This explan- 
ation of the nature of the corona reconciles itself so well with 
many facts that have been difficult to explain, such as the low 
pressure at the surface of the sun, that it gains thereby addi- 
tional strength. 
he station occupied by my temporary observatory was 
Rawlins (latitude 41° 48’ 50”, longitude 2h 0™ 44s W. of 
Washington, height 6732 feet above the sea) on the line of the 
Union Pacific railroad, because, while it was near the central 
line of totality, it had also the advantages of being supplied 
with water from the granite of Cherokee Mountain and of 
having a repair shop where mechanical work could be done. 
I knew by former experience that the air there was dry and 
apt to be cloudless; in this particular our anticipations were 
more than fulfilled by the event, for the day of totality was 
almost without a cloud and the dew-point was more than 34° F. 
below the temperature. 
The instruments we took with us were as follows and weighed 
altogether almost a ton. Ist. An equatorial mounting with 
spring governor driving clock, loaned by Professor Pickering, 
Director of Harvard Observatory. 2d. A telescope of five and 
a quarter inches aperture and seventy-eight inches focal length, 
furnished with a lens specially corrected for photography, by 
Alvan Clark & Sons. 8d. A quadruple achromatic objective 
of six inches aperture and twenty-one inches focal length, 
loaned by Messrs. E. and H. T. Anthony, of New York; to 
this lens was attached a Rutherfurd diffraction grating nearly 
two inches square, ruled on speculum metal. The arrange 
ment, with its plate holders, etc., will be designated as a photo- 
telespectroscope. 4th. A four-inch achromatic telescope with 
Merz direct vision spectroscope, brought by Professor Barker, 
from the collection of the University of Pennsylvania. 5tb. 
four-inch achromatic telescope, also brought by Professor Bar- 
er; to it was attached Edison’s tasimeter. Besides these there 
were polariscopes, a grating spectroscope, an eye slitless 
Ma pe with two-inch telescope, and, finally, a full set of 
chemicals for Anthony’s lightning collodion process, which in my 
experience is fully three times quicker than any other process. 
he arrangement of the photo-tel troscope requires iar- 
ther description, for success in the work it was intended to do, 
viz., photographing the diffraction spectrum of the corona, was 
difficult and in the opinion of many of my friends impossible. 
