124 THE HAMILTON ASSOCIATION. 
When the light of the planet is examined by the Spectroscope 
we find the lines of the solar spectrum, and this is natural since the 
planet has no light of its own and merely reflects the light of the 
sun, but we also find several absorbtion lines similar to those which 
the terrestrial atmosphere gives, and particularly those of cloud and 
water vapor. The observations of Huggins, Secchi, Respighi and 
Vogel are in agreement. At the transit of Venus in 1874, Tacchini, 
stationed at Bengal, examined with care the solar spectrum at the 
point occupied by Venus, and also inferred the existence of an 
atmosphere probably the same as ours. 2500 miles from there, at 
the Island of St. Paul, and in Eygpt, the missionaries of France and 
England made a very different but confirmatory observation, at the 
ingress and egress of the disc of Venus onthe Sun. The half of 
Venus outside the Sun was seen outlined by a faint arc of light, 
which was nothing else but the illuminated Venusian atmosphere. 
Mr. Lyman followed Venus day by day at the epoch of inferior 
conjunction, and saw its crescent elongated until the two points 
ended by passing all round the dark disc and meeting, so that the 
planet showed in the telescope the aspect of a complete ring. ‘This 
lead Mr. Lyman to complete the data, and he shows most con- 
clusively the atmosphere on Venus to be twice as dense as our own. 
This dense vapor of water and these clouds appear very well 
adapted to temper the heat of the Sun and to give to this globe a 
mean temperature, but little different from that which characterises 
our own abode. 
Attentive observation of the indentation of the surface of Venus 
shows it to be quite as uneven as that of the earth, and even more 
so. There are the Andes, Cordelleres, Alps and Pyrenees Moun- 
tains, and the most elevated summits attain the height of 
twenty-seven miles. It has even been ascertained that the northern 
hemisphere is more mountainous than the southern. Even the 
geography of Venus has been studied, but is extremely difficult, as 
the hours of pure atmosphere and possible observations are very 
rare. This will be understood, if we reflect, that it is exactly when 
Venus arrives nearest to us that she is least visible, its illuminated 
hemisphere being always turned towards the Sun. It is its dark 
hemisphere which is presented to us. The nearer it approaches us 
the narrower the crescent becomes. Add to this its vivid light and 
