XIV NOTES BY THE EDITOK 



smaller telescope was extended from the stars of the tenth to those of 

 the fourteenth degree of magnitude ; and as to fineness of definition, 

 while at Edinburgh he had never seen good images of stars in that 

 instrument, at the lower station it exhibited such clear and perfect 

 stellar disks as he had never before seen in any telescope at or near 

 the level of the sea. 



The astronomical conclusions as to the purity of the atmosphere 

 were confirmed by other observations, some of them attended with 

 unforeseen and untoward accidents. A radiation thermometer was 

 broken in a few minutes by the intense power of the sun, for which its 

 maker, in foggy England, had made no provision. Two other thermo- 

 meters that had been prepared according to Arago's ideas, and the 

 greater strength of the sun in France, though marking 180, were 

 insufficient to register the extraordinary intensity of the solar rays ; 

 for, by 10 A.M., the top of the scale was reached, and the upper bulb 

 began to fill to an unknown extent. More successful was the observa- 

 tion of the radiation of the moon by means of the Admiralty delicate 

 thermo-multiplier lent by Mr. Gassiot. 



" The position of the moon was by no means favorable, being on the 

 night of the full, 19 south of the Equator ; but the air was perfectly 

 calm, and the rare atmosphere so favorable to radiation, that a very 

 sensible amount of heat was found both on this and the following night. 

 The absolute amount was small, being about one-third of that radiated 

 by a candle at a distance of fifteen feet ; but the perfect capacity of 

 the instrument to measure still smaller quantities, and the con- 

 firmatory result of groups of several hundred observations, leave no 

 doubt of the fact of our having been enabled to measure here a 

 quantity which is so small as to be altogether inappreciable at lower 

 altitudes." 



Of the other observations made at Guajara, the abstract given in 

 the Report attests the excellence of this station for various scientific 

 researches : 



" Closely connected with radiation is the quantity of the light emitted 

 by the heavenly bodies, and this was examined frequently, in the case 

 of the sun and moon and different parts of the sky, by observations of 

 Frauenhofer's lines in the spectrum. Stokes's spectrum was also 

 examined, as recommended by the Royal Society, and was found to 

 be traceable beyond the furthest point previously ascertained else- 

 where. Means of photographing this spectrum were also prepared, 

 and some pictures of it on glass obtained, showing many of the dark 

 lines beyond II, the usual limit of vision. 



" At the upper station, with the larger telescope, the definition proved 

 admirable ; so much so, that not only once, but every night for a week, 

 I could see thut difficult test, B and C of Y Andromeda, as two distinct 



