THE SCINTILLATION OF THE STARS. 221 



the observations which I began there in the summer of 1856, during 

 a sojourn amongst them. 



3. Cairo, where Mahmoud Eflfendi, director of the observatory, 

 has commenced or will immediately commence a series of observations 

 analogous to that at Merges. 



4. Peak of Teneriffe, where Mr. Piazzi Smyth, director of the ob- 

 servatory of Edinburg, has already on one occasion spent several 

 months with a view to scientific inquiries. He has promised me that, 

 if, as he hopes, it shall be in his power to continue his researches on 

 this isolated mountain, the scintillation of the stars will be a subject 

 which will engage his particular attention. 



Four stations, however, are but a small affair for the whole surface 

 of the globe ; among others, there are certain climates and countries 

 with regard to which no information is accessible,, for example: 



The torrid zone. — There is on this zone no point of observation. 

 The Peak of Teneriffe approaches it more closely than any other, but 

 it would be important to know how the stars scintillate in the view 

 of an observer situated between the tropics, in the hottest and proba- 

 bly the most humid countries of the globe. 



Tlie southern liemispliere. — Observations made beneath the skies of 

 the other hemisphere would also possess great interest; for not only 

 would the observer be placed in very different meteorological con- 

 ditions, but he could observe certain stars which are always invisible 

 to us, among others, Achernar and Canopus. The beautiful stars of 

 that hemisphere, Sirius and Rigel, which we see only in winter, are 

 visible to the south of the equator during the hot season; they pass, 

 moreover, nearer to the zenith. It would be interesting to see how 

 the scintillation is modified by this assemblage of circumstances. 



The boreal regions. — The countries, however, which would afibrd 

 the best opportunities for valuable observations are those situated to 

 the north. It would be of consequence to know how the stars scin- 

 tillate during the cold and serene nights of Siberia, or even of Russia, 

 in Europe — what appearance they present in this respect on the polar 

 seas during those long nights which last for several consecutive 

 months. Hence, I particularly commend this study to the numerous 

 savans who live in Russia, who, from Dorpat to Archangel, from the 

 borders of the Frozen ocean to the shores of the Black sea and the 

 Caspian, might collect a numerous series of important observations. 



I commend this study also to explorers who may be called to pass 

 entire winters amidst the ices of the pole. I greatly regret that my 

 own observations did not commence ten years sooner, as I might have 

 had the opportunity of pointing out this line of inquiry- to the nu- 

 merous navigators who have traversed the polar seas in search of Sir 

 John Franklin and been imprisoned whole winters by the ice. Such 

 expeditions may be, and probably will be renewed. I take the lib- 

 erty of calling the attention of these future explorers to the scintil- 

 lation of the stars as a department of research which may prove in 

 their hands fertile in interestine: results. 



