6 TABLES AND RESULTS OF THE PRECIPITATION, 



siderable slope. It should be placed where nothing can obstruct the descending 

 snow from entering, and where no drift-snow can be blown into it. During a con- 

 tinued snowstorm the snow may be occasionally pressed down. The contents of 

 the vessel must be melted by placing it near the fire, with a cover to prevent 

 evaporation, and the water produced poured into the gauge to ascertain its quantity, 

 which must then be entered on the register." 



A description of the conical rain-gauge is given in Silliman's Journal of Science 

 and Arts for April, May, and June, 1832. 



Directions issued July 1, 1844, from the Surgeon-General's Office, hold the 

 senior medical officer on duty at each military station officially responsible for the 

 accuracy- of the meteorological observations made at the station. 



The following additional direction is given in the introduction to the Army 

 Meteorological Register from 1843 to 1854 inclusive (Washington, 1855): "At 

 every fall of rain, snow, hail, or sleet the time of its commencement and end will 

 be recorded, and the quantity which fell is indicated by the rain-gauge." 



Rain-gauges adopted by the Smithsonian Institution. — The following is an extract 

 from the " Directions for Meteorological Observations adopted by the Smithsonian 

 Institution, for the first-class Observers," in the annual Smithsonian Report for 1855 

 (Washington, 1856): "The ombrometer, or rain-gauge, is a funnel accompanied by 

 a graduated cylindrical glass vessel, and by a reservoir. It should be placed in an 

 open space. Trees, high buildings, and other obstacles, if too near, may have a 

 considerable influence in increasing or diminishing the quantity of rain which falls 

 into the funnel. The surface of the receiver should be placed horizontally about 

 six inches above the ground." Next follows a simple mode of establishing this 

 gauge, accompanied by a wood-cut of the same. Directions for observing are given 

 as follows : — 



"To make the observation, remove the funnel and pour the water from the jug 

 into the large graduated glass cylinder. The opening of the funnel being one 

 hundred square inches, one inch of rain in depth gives one hundred cubic inches 

 of water; and each division of the glass containing a cubic inch of water, each of 

 them represents a hundredth of an inch of rain fallen into the ombrometer. These 

 degrees are large enough to permit us to estimate the thousandths of an inch, etc. 

 etc. 



"The snow-gauge 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 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-gauge, 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 gauge, 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 operation 

 may be facilitated by placing on the ground a platform of strong board or plank, 



