320 REPORT— 1851. 



be more strikingly shown than by the curves produced from the discussion 

 of the present catalogue referred to hereafter. 



Where the volume and page of an author are not quoted, the event will 

 be found in its chronological order in the note referred to. 



Where access to the original work has been impossible, and we have 

 merely quoted from some other compiler or narrator, we are only responsible 

 for having accurately transcribed ; our experience seems to show that other 

 transcribers have usually been very accurate. 



In the characteristic expressions used in the fourth and fifth columns, and 

 transcribed from other authors, they must be taken with reference to degree, 

 as only giving the author's own opinion of the fact, whatever it may be, and 

 such expressions are often extremely difficult, either to attach a true value 

 to or compare together. Thus such phrases as " violent," " very violent," 

 depend much for their import upon where and by whom they were used. 

 An earthquake described as " very violent" by an inhabitant of Norway or 

 of Great Britain, might seem but a very slight and insignificant affair to a 

 dweller at Lima or Quito, though both were equally discreet and trustworthy 

 observers. 



There has been also experienced much difficulty in some cases of long- 

 continued vibratory jars at a given locality, such as those of Bale, East 

 Haddam and Comrie, &c., in deciding whether one such epoch was to be re- 

 cognised as one earthquake, or as more than one. 



Any further observations however will be best reserved for the conclusion 

 of the catalogue, when referring to the discussion by curves of the distribution 

 of earthquakes in time, and by the large map of their distribution in space. 



Letter from Professor Henry, Secretary of the Smithsonian InstitU' 

 tion at Washington, to Colonel Sabine, General Secretary of the 

 British Association, on the System of Meteorological Observations 

 proposed to be established in the United States. 



Smithsonian Institution, 

 Washington, March 22, 1851. 



Dear Sir, — The meteorological system in the process of being established 

 in the United States, is intended to embrace as far as possible the whole area 

 of the North American continent, including the Isthmus of Central America, 

 the West India Islands, Bermuda, and Newfoundland. 



It is to consist of three classes of observers : — 



I. Those without instruments, to record — 



1. The changes in the aspect of the sky. 



2. The direction and approximate force of the wind and the time of 



its changes. 



3. The beginning and ending of rain, snow, &c. 



4. The appearance of the Aurora Borealis. 



5. The time and direction of approach, and other phsenomena of 



thunder-storms. 



6. The registration of phaenomena relative to plants and animals, 



such as the first appearance of leaves and of flowers in plants ; 

 the dates of appearance and disappearance of migratory or hy- 

 bernating animals, as Mammalia, Birds, Reptiles, Fishes, Insects, 

 &c. ; the times of nesting of Birds, of moulting, and littering of 



