20 



OMBROMETER. 



and the quantity of water produced measured by pouring it into 

 the glass cylinder. It need hardly be said, that if rain and snow- 

 fall the same day, no account will be taken except of what the 

 snow-gage receives, unless the ombrometer has been observed 

 separately after the rain, and the snow-gage after the snow. 

 Care must be taken, in these cases, not to count twice the same 

 quantity of fallen water. 



The rain-water and melted snow-water must be separately 

 entered in the journal in the columns reserved for each. 



During abundant rain-falls, it is well to measure the water 

 more than once a day, or at least immediately after the rain ; 

 and the quantity of the rain fallen, together with the time it has 

 lasted, is to be noted separately in the column of remarks. 



When it freezes, it will be necessary to protect the receiver by 

 filling in the interior of the barrel with straw. 



[A series of observations have been made at the Smithsonian 

 Institution with rain-gages of different sizes and different forms, 

 the result of which, as far as the observations have been carried, 

 is to induce a preference for the smallest gages. The one which 

 was first distributed by the Institution and the Patent Office to 

 the observers, is represented in Fig. 10. It consists of the 



Fig. 10. 



funnel a, terminated above by a cylindrical brass ring, bevelled 

 into a sharp edge at the top, turned perfectly round in a lathe, 

 and of precisely five inches diameter. The rain which falls 

 within this ring is conducted into a two-quart bottle, b, placed 

 below to receive it. To prevent any water which may run down 

 on the outside of the funnel from entering the bottle, a short 



