466 KANSAS CITY REVIEW OF SCIENCE. 
ctrascope of lines were visible beyond H and Hj. The solar corona 
was not seen, nor were any lines discernible in the spectrum of the zodiacal light, 
although that light was sufficiently bright to be very obvious when the Moon was 
eight days old. 
Dr. Copeland made also several interesting meteorological observations. 
Black bulb temperatures up to 205-5° F. were recorded, this being the limit of 
the tube of the instrument, and not the actual maxitnum. With the black-bulb 
thermometer more than 13° above the local boiling-point, the wet-bulb was below 
the freezing-point. At Arequipa (7,500 feet), the relative humidity of the air 
was as low as 20 per cent, and not much higher at other stations. The author 
believed that an observatory might be maintained with great facility at a height of 
between 9,000 feet and 12,000 feet, the night temperature being little below the 
freezing-point at any season. Beyond that height an increased elevation of 150 
feet roughly corresponded to a fall of the thermometer of 1° F., and a depression 
of the barometer of i-ioth inch, so that at 15,000 feet very arduous winter condi- 
tions were encountered. 
Professor Janssen gave an account of his observations on the solar corona, 
made at Caroline Island during the recent solar eclipse. He stated that in 1870 
he had seen, for the first time, dark lines in the spectrum of the corona — indicat- 
ing, probably, the existence of matter capable of reflecting the solar light. This 
observation had been confirmed by some observers, while others had failed to 
obtain evidence of it. He thought that the failure was due to the fact that the 
telescopes used by most observers had too small an aperture compared with their 
focal length, so that the amount of light received by the slit of the spectro- 
scope was very small ; the luminosity of the corona being very feeble. Dr. Jans- 
sen used a lens of 50 centimetres aperture, with a focal length of 150 centimetres 
to form the image on the slit of the spectroscope, which was one which admitted 
a large quantity of light. By means of an ingenious arrangement, it was possi- 
ble to observe with one eye at the spectroscope, while the other noted through 
the finder the part of the corona examined. Dr. Janssen found a complicated 
spectrum with many dark lines. In the course of his paper he referred to the 
measurement by photographic means of the intensity of Ught, and stated that 
the corona was about as bright as the full Moon. Dr. Schuster thought that the 
differences observed at different eclipses, as to the existence of dark lines, might 
be real, and not due to want of illumination. During the eclipse in Egypt he 
had succeeded in photographing G as a dark line. He agreed with Dr. Janssen 
in attributing the reflection of the solar light to meteoric matter, and pointed out 
that near the Sun there were no lines, so that there the matter was self-luminous. 
■Prof. Stokes was inclined to refer the reflection to the action of small particles of 
matter shot out from the Sun in the form of vapor, but condensed at a distance 
from its surface, forming, as it were, clouds of minute particles. — Knowl 
