34:0 On the determination o/^ differences of Longitude. 



think the extreme discrepancy of different nights' work will 

 amount to only a small fraction of a second. It appears to 

 me that this mode of determining differences of longitude 

 must supersede every other method between places which are 

 connected by a telegraphic wire. The observations can be 

 repeated indefinitely, and I think the longitude can be deter- 

 mined with a precision fully equal to that of the local times. 

 I presume the same cannot be said of any other method yet 

 practised. I have not heard of this method being tried in 

 any part of Europe, though the application is very obvious. 

 Can you inform me of any such trials ? 



In my former correspondence with you, and in my printed 

 papers, I have more than once alluded to the importance of a 

 combined movement in this country for meteorological obser- 

 vations. I am happy to say that the prospect of such a com- 

 bination is brightening. You are probably aware that the 

 Smithsonian Institution has been organized, and Prof. Joseph 

 Henry has been placed at the head of it. The plan of orga- 

 nization is to appropriate c§^l 5,000 a-year to the promotion 

 o^ original researches. Prof. Henry is disposed to include in 

 this plan a grand meteorological campaign, to continue for 

 three years, — to cover the entire area of the United States 

 with the greatest possible number of observers : we want 300, 

 and I think they could be obtained. I have been drawing up 

 a paper for Prof. Henry which will be placed before the 

 Smithsonian Institution, and also before Congress the coming 

 winter. I think the plan will be carried into execution, pro- 

 vided we can obtain the co operation of the British Govern- 

 ment. You know from the papers which I have sent you that 

 our great storms frequently extend far to the northward of 

 the United States. When the centre of a storm travels along 

 the valley of the St. Lawrence, its margin often extends to the 

 Gulf of Mexico. Observations spread over the entire United 

 States would frequently include only half the area of a violent 

 winter storm ; and this is the class of storms from which most 

 is to be expected, because their phaenomena are most strongly 

 developed. Unless therefore we could obtain simultaneous 

 observations from the British possessions on the north of us, 

 we should feel that our observations were deprived of more 

 than half their value. Will you not see if the I3ritish Govern- 

 ment and the Hudson's Bay Company cannot be induced to 

 co-operate with us ? What I propose is, that at every go- 

 vernment station a register should be kept for a period of one, 

 two, or three years. I should hope 100 such stations could 

 be procured. The first cost of the instruments would not be 



