Vlll NOTES BY THE EDITOR 



dom is continued, and promises to develope itself into an important 

 branch of commercial astronomy. Two noteworthy facts are mentioned 

 in the report : one is, that the hill on which the observatory stands is 

 in a state of tremor, whereby the trough of mercury in which stars 

 are observed by reflection, is so much agitated as to make observation 

 impossible. To overcome the difficulty, a well ten feet deep was dug, 

 and filled with "incoherent rubbish," on which the trough was placed, 

 resting on stages suspended by strips of caoutchouc, " leaving the 

 image practically," as Mr. Airy says, " almost perfect." The other is, 

 that fluctuations were found to occur in the zero of the altazimuth 

 circle, and simultaneously with, a sudden and marked change of atmo- 

 spheric temperature a phenomenon which the Astronomer Koyal can- 

 not account for, "except by supposing that in sudden atmospheric 

 changes the gravel rock of Greenwich Hill does suddenly change its 

 position." 



During the past year the trigonometrical survey of Great Britain, 

 commenced in 1784, has been completed. The object which the 

 government had chiefly in view in 1784 was the determination of the 

 difference of longitude between the observatories of Greenwich and 

 Paris. The geodetical problems have been satisfactorily solved, but the 

 survey has assumed a wider scope as it advanced, and its important 

 results, both in scientific and national points of view, are familiarly 

 known. 



In India, under the auspices of the British Government, a trigono- 

 metrical survey has been undertaken, and above fifty sheets of an 

 Indian Atlas, based on the survey, have been already published. 



In a discussion which took place at the Albany Meeting of the 

 American Association, relative to the utility and comparatively small 

 expenditure of the coast survey, Prof. Alexander stated that he had 

 taken pains to compute the cost, square mile by square mile, of that 

 work, and had found that its cost did not exceed that of the crude 

 surveys of the public lands. 



At the last Meeting of the American Association, Mr. W. P. Blake 

 called attention to the very gross inaccuracies existing in a map recently 

 published by M. Marcou, of France, of the geology of the region 

 between the Mississippi and the Pacific. Mr. Blake enumerated 

 several of the prominent errors, among them the representation of the 

 rocks of San Francisco as granitic and metamorphic, they being tertiary, 

 and making Fremont's Peak into a volcano, when in his official report 

 it was clearly and fully stated to be granitic. Proofs were brought for- 

 ward to show that the formation called Jurassic, &c., by M. Marcou was 

 not so, but was cretacious. There was no evidence by fossils to show 

 that the triassic formations were found under the cretacious ; they 

 might be, but no fossils had been obtained, and the age could not yet 



