No. 1070, Vol. 42] 



NA TURE 



thought practicable to re-occupy Foster's station at 

 Lemon Valley. Here at Ascension the sea-level station 

 at Garrison is already complete ; and, as I write, Mr. 

 Preston and Prof. Bigelow are taking quarters near the 

 summit of Green Mountain for the second station, near 

 the spot occupied by Foster sixty years ago, elevation 

 between two and three thousand feet. Auxiliary magnetic 

 work is undertaken at both these upper-level island 

 stations. Between Ascension and New York but one 



prolonged stop is at present contemplated — at Bridge- 

 town, Barbados — where magnetics will be done, and 

 gravity-work, if practicable. Also, Bermudas may be 

 included, but that is perhaps unlikely. In addition to the 

 bearing of this work on terrestrial physics and geologic 

 theories, it is worthy of note, in passing, that all these 

 stations, including Washington, where swings are made 

 both before the departure of the Expedition and after its 

 return, lie within a narrow great-circle belt, which can at 



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130 



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•••••• ••••• •••••• 



10 



110 



Control-sheet of the Pneumatic Coinmulator between the looth and 120th seconds of Totality. 



any time be continued on through the United States and 

 Canadas and Alaska, forming an extraordinary stretch of 

 gravimetric survey. 



Regarding the eclipse and the stay of the astronomers 

 at Cape Ledo, it has to be said, to our great regret, that 

 the direct photo-heliograph of 40 feet focal length was the 

 only instrument with which eclipse-records could be 

 secured. These were photographs of the partial phases, 

 over 100 in number, obtained between clouds. The in- 

 strument was built under the immediate supervision of 



Prof- Bigelow, and has, among other peculiarities, a 

 skeleton tripod-mounting which will be fully figured in the 

 definitive report of the Expedition. It has been proven 

 practicable to dispense with the heliostat mirror, always 

 the weak point in the horizontal photo-heliograph ; and 

 to manipulate readily a camera long enough to produce a 

 4i-inch solar image direct : and this, too, by means of a 

 mounting easy to transport and to set in position. The 

 photographs were taken in groups of ten, on circular 

 plates of 22 inches diameter. The apparatus auxiliary 



