MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 27 



mit is reserved for 1896. The season was not favorable, and M. 

 Janssen congratulates M. Bigourdan on tlie courage, activity, and 

 devotion wliicli lie showed in the "rude campaign." Dr. de Thierry 

 had also made a "difficult and courageous" ascent to the summit, 

 where he stayed for an entire day, engaged in experiments on atmos- 

 pheric ozone and on microbiologj^. Thanks to the courage, the force, 

 and the experience of the porters, all the parts of the 12-inch equa- 

 torial which is to be installed at the summit have been transported 

 amid "the chaos of the glacier" and stored in safety without an acci- 

 dent to the men. 



Leaving Chamounix on September 26, M. Janssen himself made 

 an ascent to the summit to engage in observations on the presence of 

 water- vapor in the sun (which he found to be absent, all the conditions 

 being favorable for his spectroscopic work,) to examine the storage of 

 the parts of the equatorial, and to inspect the self -registering meteoro- 

 logical instrument (which had ceased to act because of lack of stability, 

 and was corrected). 



M. Janssen examined the observatory also, to determine whether it 

 had suffered displacement since its installation. It has moved slightly 

 towards Chamounix, but this movement took place in 1893-94. The 

 construction can be levelled at any time by the jack-screws with which 

 it is provided. The problem of building on the summits of high 

 mountains is then in a good way of solution, and M. Janssen points 

 out that the high and snowy summits of the Andes, Himalaya, etc., 

 " actuellement si importantes pour les progres de la Meteorologie et de 

 r Astronomic," are open to occupation so soon as we have learned to 

 place buildings and instruments upon them which are appropriate to 

 the conditions to which they will be subjected. In a foot-note M. 

 Janssen recalls the fact that in 1891 M. Yallot pointed out that the 

 summit of Mt. Blanc was a true glacier, and that such a site for an 

 observatory should be rejected. The whole history of the Mt. Blanc 

 station is not yet written, and it is at least possible that the very 

 ingenious arrangements for the foundations of the summit station, 

 which are entirely satisfactory at present, may need modification at a 

 future time, under changed conditions. The summits of high moun- 

 tains are certainly liable to serious changes, as many observations have 

 abundantly proved. 



In a note of 1890, Professor Cornu describes observations made by 

 Dr. Simony in 1888 on the peak of Teneriff e, which had for their object 

 the registration of the solar spectrum by photography, and which have 

 a bearing on observations to be made on Mt. Blanc. It is of importance 

 to know what the limits of the solar spectrum are, and, on the other 

 hand, the observation of these limits at different altitudes constitutes 



