XII TABLES AND RESULTS OF THE PRECIPITATION 



atiuii of the scale is by luindredtlis of an inch for the first three-tenths of an inch, 

 and above that by tenths and half-tenths. Parts of degrees will be measured by the 

 eye, and set down in decimals. If a rain continue for any length of time, the quantity 

 in the gauge will be measured at suitable intervals, before the water rises high in it, 

 and the measurements summed up at the close. 



" In fi-eezing weather, when the rain-gauge cannot be used out of doors, it must be 

 taken into the room, and a tin vessel will be substituted for receiving the snow, rain, 

 or sleet that may then fall. This vessel must have its opening exactly equal to that 

 of the rain-gauge, and widen downwards to a sufficient depth, with a considerable 

 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 continued snow- 

 storm the snow may be occasionally pressed down. The contents of the vessel must 

 be melted by placing it near the tire, 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, fi-om the Surgeon-Greneral'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 re- 

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



Rain-gauges adopted hy 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 4855 

 (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 con- 

 siderable 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 hun- 

 dred 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 



