OMBROMETER. 19 



placed in the barrel itself, if it is of sufficient size. They must 

 be placed in a reversed position, on two upright pegs, to let 

 them drip out. As soon as the observation is made, it should 

 be noted in pencil, not trusted to the memory; and written in 

 the journal upon entering the house. 



SNOW-GAGE. 



Observation. — The snoiv-gage should be supported vertically, 

 in an open place, between three short wooden posts, its opening 

 being about two feet from the ground. It should be employed 

 in the following manner : — 



When only a very small quantity of snow falls, or of snow 

 alternating with rain, or of dry and fine snow, driven by the 

 wind, it should be collected in the snow-gage, as would be done 

 in the ombrometer. But when the snow falls in a sufficient 

 quantity to cover the ground more than an inch deep, the vessel 

 must be emptied, and plunged, mouth downwards, into the 

 snow, until the rim reaches the bottom. A plate of tinned iron, 

 or a small board, may then be passed between the ground and 

 the mouth of the gage, and the whole reversed. In this way a 

 cylinder of snow, of which the base is superficially one hundred 

 inches, will be cut out, and received into the vessel. The opera- 

 tion may be facilitated by placing on the ground a platform of 

 strong board or plank, two or three feet square, on which the 

 snow is received. 



The place selected for this purpose must be one where the 

 snow has not been heaped up, or swept away by the wind, and 

 where it presents, as near as possible, the mean depth of the 

 layer that has fallen. In order to take only the snow which 

 may fall in the interval between two observations, the board 

 should be swept after each measurement, and the place desig- 

 nated by stakes. 



Reading. — In the reading of the graduated vessels, the general 

 surface of the liquid must be considered as the true height, and 

 not the edges, which are always raised along the walls of the 

 vessel by capillary attraction. 



The collected snow must be melted by placing the gage, 

 covered with a board, to prevent evaporation, in a warm room; 



