S. P. Langley— Observations on Mount Etna. 33 
Art. IIlT.—Observations on Mount Etna; by S. P. LANGLEY. 
Durine the winter of 1878, in the course of a visit to Europe, 
I spent some time upon Mount Etna, and at the request of Cap- 
tain Carlisle P. Patterson, the Superintendent of the United 
States Coast Survey, gave attention there to the character of 
the astronomical vision, in order to enable comparisons to be 
made with observations taken under similar conditions in our 
own territories. I have thought that in view of the present 
nearly in ee ede to the increase of optical power, ha 
to be so nearly a barrier to any rapid progress, that attention 
shores and islands of the Mediterranean, and particularly of 
Sicily, as being on the whole superior to that of Northe 
Europe, and in Sicily, Mount Etna has not only long been dis- 
pr a for the extraordinary extent of the prospect, undis- 
turbed by haze, but by its recent selection as a site for a 
mountain observatory by the Italian authorities guided by the 
Very concurrent testimony points to the atmosphere of the 
competent judgment of Professor Tacchini. This was the 
Am. Jour. orxsieeer Series, Vou. XX, No. 115.—Juxy, 1880, 
