100 , TEANSIT OF TENUS. 



The predicted times of these phenomena given in the English 

 Nautical Almanac are very far from the observed times. The 

 times given are : — 



1st contact. h. m. s. m. s. 



From jSTautical Almanac ... 11 52 18 



Observed 11 55 23 = 3 5 after F.A. 



2nd contact. 

 From Jfautical Almanac ... 12 21 12 



Observed 12 23 59 = 2 47 after N. A. 



3rd contact. 

 From Nautical Almanac ... 3 55 54 



Observed 3 54 40 z= 1 14 before N. A. 



4th contact. 

 From Nautical Almanac ... 4 25 12 



Observed 4 24 27 = 45 before N. A. 



h. m. s. 

 The whole predicted interval, 1 to 4 contacts ... 4 33 54 

 The whole observed interval, 1 to 4 contacts ... 4 29 4 



That is, 3m. 50s. less than predicted. 

 The whole predicted interval, 2 to 3 contacts ... 3 34 42 

 The whole observed interval, 2 to 3 contacts ... . 3 30 41 

 That is, 4m. Is. less than predicted. 

 This is a different result from what would have been expected 

 on comparing intervals, for it is generally assumed that external 

 contacts cannot be observed within 10 or 15 seconds, and the 

 above seems to show that the interval between external contacts 

 was comparatively longer than the internal interval. If we take 

 the mean of the times observed for 2nd and 3rd contacts we get — 



h. m. s. 



2nd 12 23 57-32 



3rd 3 54 3992 



Difference 3 30 42-60 



Whole predicted interval 3 34 42-00 



3 59-40 

 — which makes the interval 2 to 3 even greater than my own 

 observations, and seems to point to an error in the whole predicted 

 interval as well as in the times of the phenomena. 



Turning now to the physical phenomena observed, there are 

 several of them very interesting and important that will repay a 

 little consideration, and first in regard to the hlach drop so called, 

 that is, a ligament or connection that it was asserted formed when 

 the limb of Yenus was on that of the sun. The explanation of the 

 black drop given by Mr. Stone, now Astronomer Eoyal at the 

 Cape of Good Hope, seemed so thoroughly satisfactory that I 



