SCIENTIFIC NOTES. 



By H. C. Russell, Esq., M.A., Government Astronomer, 



[Read he/ore the Royal Society, 3rd November, 1875. j 



When our Council, last Wednesday, asked me to say something 

 about my recent trip to Europe, I consented with some reluctance, 

 not because I would rather not speak, for I am glad to be able to 

 afford information to the members of the Society, but because I 

 was afraid that I should not be able to interest you while the illus- 

 trations of nine-tenths of the facts I have collected are somewhere 

 on the Pacific. 



On the last occasion I had the pleasure of saying anything to 

 the members of the Royal Society, it had reference to the transit 

 of Yenus, and probably, though most of what transpired while 

 I was in England has already been published here, a few words 

 on that subject may be said now. You are aware that at the 

 time our photos, and drawings of all the phenomena of the transit 

 were exhibited to the members of the Royal Astronomical 

 Society, they were believed to be the best and most complete ; 

 so far as I have been able to learn they still hold that position 

 for definition on the edges of the sun and planet, which are the 

 essential points, but they are not so dense in silver as some 

 others which were exhibited afterwards. This is easily explained. 

 Prior to the transit, it was pointed out that to intensify any of 

 the photos, would be to spoil them, for the deposit of silver 

 would take place at the edges as well as in the thickness, and 

 considerable uncertainty would in this way be introduced into the 

 value of the picture ; in fact, it was understood that, as the density 

 of the pictures would vary from atmospheric and mechanical causes, 

 the application of an intensifier to bring them up to the mark would 

 make the edges of some creep more than others, and make them 

 very unsatisfactory, if not useless for the purpose of measurement. 

 We, in the Colony, carefully abstained from intensifying any photo, 

 and left them exactly as they were taken ; others have departed 

 from this important principle, hence their negatives have more silver 

 than ours ; how far this will affect their value remains to be seen 

 when they come under the micrometer. It is to be hoped that they 

 will all be better than is expected, for it is a very general 

 opinion that the times of contact will not prove so satisfactory 



