METEOROLOGY. 



DIRECTIONS 



FOE 



METEOROLOGICAL OBSERVATIONS, 



ADOPTED BY THE SMITHSONIAN INSTITUTION, FOR THE FIRST CLASS OF OBSERVERS. 



The following directions were originally drawn up for tlie use of 

 the observers in correspondence with tlie Smithsonian Institution, by 

 Professor GuYOT, of the College of New Jersey, Princeton, and are 

 now reprinted, with a series of additions, for mose general distribution. 

 The additions are indicated by brackets, [ ]. 



Secretary S. I. 



PLACING AND MANAGEMENT OF THE INSTRUMENTS. 

 THERMOMETER. 



Placing. — Place the thermometer in the open air, and in an open 

 space, out of the vicinity of high buildings, or of any obstacle that 

 impedes the free circulation of the air. It should be so situated as to 

 face the north, to be always in the shade, and be at least from nine to 

 twelve inches from the walls of the building, and from every other 

 neighboring object. The height from the ground may be from ten to 

 fifteen feet, and, as far as possible, it should be the same at all the 

 stations. The instrument should be protected against its own radia- 

 tion to the sky, and against the light reflected by neighboring objects, 

 such as buildings, the ground itself, and sheltered from the rain, snow, 

 and hail. The following arrangement will fulfil these requirements, 

 (figure 1.) 



Select a window situated in the first story, fronting the north, in a 

 room not heated or inhabited ; remove the lattice blinds, if there be 

 any, and along the exterior jambs of the window place perpendicular- 

 ly two pieces of board, (a h—a' U), projecting to a distance of from 

 twenty to twenty-four inches from the panes. At half this distance,^ 

 ten or twelve inches from the panes, and at the height of the eye of 

 the observer, when in the chamber, pass from one piece of board to 

 the other two small wooden transverse bars, (c d, d d' ,) each an inch 

 broad, for the purpose of supporting the instruments. Upon the outer 

 edge of the boards fasten in the usual way (H H) the latticed blinds 

 which were removed from the jambs, or two others provided for the 

 purpose. That blind, behind which the instruments are to be placed, 

 is to serve as a screen, and must be fastened, almost entirely closed, 

 so as make a little more opening ; the other will remain entirely open 

 to allow a free access of air and light, and is not to be closed except in 

 great storms. The whole must be covered with a small inclined roof 



