360 
POPULAR SCIENCE REVIEW. 
finishing of the observatory would he sufficient to furnish the 
funds to meet all engagements. The work was pushed rapidly 
forward. In February 1845 the great telescope safely reached 
the city ; and in March the building was ready for its reception.” 
Unfortunately, just at this time, when his private means were 
exhausted, Professor Mitchel’s professorship was brought, in a 
very summary manner, to a temporary close, in consequence of 
the college edifice being burned to the ground. To recruit his 
means without abandoning the cause of astronomy, he gave 
courses of lectures in the chief cities of the United States, 
meeting with well-deserved success. 
The observatory thus erected achieved useful, though not 
very striking results. An observatory which was erected a year 
or two later took so quickly the leading position, so far as the 
actual study of the heavenly bodies was concerned, that the 
progress of the Cincinnati astronomers, as indeed of most of 
the astronomers of the United States, received less attention 
than otherwise might have been the case. I refer to the Ob- 
servatory at Harvard (Cambridge, Mass.). Here one of the first 
equatorials ever made by Merz was erected ; and by means of it 
W. C. Bond and his son Greo. P. Bond made highly interesting 
additions to astronomical knowledge. The seventh satellite of 
Saturn (eighth and last in order of discovery) was detected, 
the dark ring rediscovered and found to be transparent ; im- 
portant drawings of nebulae were made, and many other ob- 
servations were effected, under the administration of the Bonds. 
Later, under Professor Winlock, the Harvard Observatory has 
been distinguished by the excellence of the mechanical arrange- 
ments adopted there, and by M. Trouvelot’s admirable draw- 
ings of solar spots and prominences of the planets Jupiter and 
Saturn, and of various details of lunar scenery. 
In passing, I may note that at Harvard, as indeed elsewhere 
in America, others than professed astronomers have achieved 
very useful astronomical work. As Professor Mayer, of the 
Stevens Institute, Hoboken, has turned his marvellous ingenuity 
in devising new methods of physical research to astronomical 
inquiries, so Professor Cooke of Harvard, whose special subject 
is chemistry, made a most important astronomical discovery, 
which has since been ascribed to Janssen, who, later (though 
independently and by another method) effected it. Professor 
Cooke made a series of observations on those bands in the 
solar spectrum which are due to our own atmosphere, with the 
object of ascertaining whether they are due to the constant con- 
stituents of the air, or to the aqueous vapour which is present 
in the air in variable quantity. Combining hygrometric with 
spectroscopic observations, he found that when the air is moist 
these bands are more clearly seen than when the air is dry, and 
