266 



Correspondence of J. Nickles. 



After completing the design with every possible care, M. Secchi has had 

 copies taken by photography, one of which he has sent to the Academy. 

 The crater or annular mountain. has two circuit walls. The outer, which is 

 the lowest, has a diameter of about 48 seconds (one second corresponds to 

 1-820 meters) ; the inner, the true border of the crater, has a mean diam- 

 eter of 38 seconds, and has a peak, somewhat elevated, on its western 

 side. The inner area is 20 seconds across. The interior has a steep es- 

 carpment around, and a triple circuit of broken rocks and a great number 

 of large masses piled up at the foot of the escarpment, as if they had 

 fallen from above. There are two great depressions in the north and south 

 borders of the crater ; and it is remarkable that in the direction of this 

 line, outside, both north and south, there are some small craters. 



After having established the perfect resemblance which exists between 

 the volcanic mountains of the environs of Rome and the lunar moun- 

 tains,* (comparing with the chart of the Roman territory made by the 

 French officers), M. Secchi adds, k 'The question whether volcanic action 

 in the moon is actually extinct, can be answered only after there shall 

 have been made a map of the moon's surface for a given period with the 

 utmost accuracy and on a large scale." It is to help onward this project, 

 that he has undertaken the work above described. 



Meteorological System of France. — Notwithstanding the enemies of 

 meteorological observations alluded to in a former communication, the 

 system for France is now nearly established. The telegraph reports to 

 the director of the Paris Observatory, M. Leverrier, the observations made 

 at different points over the empire. All the stations are supplied with in- 

 struments which have been compared with great care. The instrument 

 which has undergone the most modification is the barometer. The ba- 

 rometer of Fortin, which is the most perfect of all, has not been adopted, 

 because it works well only in the most experienced hands, and the deter- 

 mination of the atmospheric pressure with it is an experiment in physics 

 of great delicacy rather than a direct observation. The instrument used 

 is very simple and gives the pressure of the air at a single reading, the 

 corrections being contained in tables. 



Besides the corps of amateur meteorologists, a regular system of ob- 

 servers under administrative direction was required, which should be 

 perpetual and independent of the direct action of those constituting it. 

 This is now realized, the stations being established within the telegraphic 

 bureaus, the assistants in which have had a good education. The num- 

 ber of stations is now 25, and they are situated in the principal basins of 

 France. Each person in charge of a station is required to make three ob- 

 servations a day, but may make more at his pleasure. These observa- 

 ations are registered in a book kept at the station ; and at 1 or 8 o'clock 

 in the morning they are reported by the telegraph according to a con- 

 certed formula, to the Paris Observatory, where they are recorded on spe- 

 cial registers, to be tabulated and published. 



* The more thoroughly the volcanic mountains of the moon are studied, the more 

 completely do they sustain the resemblance to the great boiling lava craters like 

 Kilauea of the Hawaian Islands, as pointed out by the writer in an article on the 

 Volcanoes of the Moon, in this Journal, volume ii, 2nd Series, page 335, 1846. — 



J. D. D. 



