for the year 1875. xxxvii 



difficulties of observing, the Transit was generally well 

 seen. 



Independently of obtaining the distance of the sun from 

 the earth, the late Transit has disclosed physical phenomena 

 of great value. The celebrated Italian spectroscopist 

 Secchi, observing at Maddapore, in India, has determined 

 the presence of aqueous vapour in the atmosphere of Venus, 

 and Janssen, the eminent French observer, found that the 

 internal contact, as observed by eye through a telescope 

 furnished with a bluish shade, took place some seconds 

 before the same phase was depicted photographically, thus 

 showing that the sun built up by the blue rays was smaller 

 than the sun built up by the particular rays which, in the 

 telescope employed, produced white light. 



Concerning the Total Eclipse of the Sun in April last, but 

 little can be stated ; the expedition to Siam has proved at 

 best, according to accounts to hand, only a partial success ; 

 the attempt to photograph the spectrum of the corona, from 

 which so much was hoped, having failed. But even from 

 our failures there is always something to be learned. 



Let us now pass from these astronomical subjects to 

 another item of prominent scientific importance, the 

 Challenger expedition, rendered additionally interesting to 

 us by the visit of the ship to these shores. It is pretty 

 generally known that earlier cruises and voyages, with 

 objects similar to those of the Challenger expedition, have 

 prepared the way for the latter greater undertaking, and 

 that the work still in progress by the Challenger is a 

 continuation and expansion of that commenced by the 

 Lightning and carried forward with marked success by 

 H.M.S. Porcupine. The cruise of the Lightning extended 

 over a period of six weeks only, examining the space 

 between Scotland and the Faroe's. Then followed the 

 voyage of the Porcupine, over a far more extensive area, 



