REPORTS FROM THE SECTIONS. 273 
they were magnified by the oxy-hydr ogen apparatus, and rewritten 
by newspaper authorities and others interested therein. pwards 
of 100,000 hog cara: were received in Paris during the siege by 
these mean 
In astr a Heel we find the gare: hand of photography. 
It seems to have in this case a two purpose—obtaining the 
images of the *hhasenty bodies for oe purpose of measure- 
ment, and for producing pictures of some of these bodies with 
collodion process for the same purpose in 1860, and at the 
present time all the European Governments use it in connec- 
tion with astronomy. The Scientific American says :—“ Astro- 
nomical photography has recently assumed a higher place than as 
a mere mode of reproduction of the images seen through the 
telescope. It has, in fact, become an important means ‘of dis- 
covery ; and the researches of Professor Janssen of Paris, has shown 
that photographic pictures reveal phenomena otherwise perfectly 
invisible, It was through such prints that he discovered the 
photospheric network round the sun.” ree proof of its utility 
was furnished during the late transit of Venus, and another not 
less important exists in the fact, that the British aa 
ment supervision. The French Government, however, ‘possens 
the most im mportant set of photo-astronomical instruments in their 
splendidly fitted-up ai at Meudon Observatory, near Paris. 
re daily photographs are taken of tlre sun, the average exposure 
being one-twelfth of a second for an image 3%; of an inch in 
(liameter. Sir George Airy gives another proof of its utility when 
he says, “The computation ‘of the photographie records o 
barometers, from 1854 to 1873, has so far advanced that it is 
asserted positively that thoes is no trace of lunar tide in the 
atmosphere, but that there is a reaiege'é -marked semi-diurnal tide, 
i 
graphy, (Vide before the American Philoso 
Society, J = 20, uSTT) 7.) Professor Janssen’s photographs of the 
sun are now causing as much excitement as De la Rue’s photo- 
graphs of the moon ‘lid some years ago. 
_ , Another important use to which eer i * put is 
hahaa its rigorous exactness re particu. 
eras dP 
Hs! tm loto ‘bo ably proved hy moms In 
