Description of an improved Rain Gage. 327 



The following is a description of a Rain Gage construct- 

 ed on principles, by the help of which, the quantity of rnin 

 that falls into it can be accurately determined in inches of 

 altitude, without being affected by the causes of error allu- 

 ded to above. 



An essential part of the Rain Gage is a prismatic vessel, 

 Fig. 4 &; 5, PI. 2. whose top and bottom are, each 10 inches 

 square, inside measure, with any convenient height. 



This is all that is necessary for occasional experiments, as 

 for instance, to determine the quantity of rain, snow or sleet, 

 that may fall in winter when the evaporation is incon- 

 siderable, or the quantity of rain that falls in a single show- 

 er, at any other season. But to answer all purposes, it must 

 be provided with a cover, in the centre of which is inserted 

 a funnel, whose top has the same area, as that of the lop or 

 bottom, of the prismatic vessel above. To prevent evapora- 

 tion the orifice of the funnel is furnished with a valve against 

 which a weak spring, attached to the inside of the cover, 

 presses with a force just sufficient to close it, but which is 

 overcome by the weight of a few drops of rain. It is evi- 

 dent that in a shower the water will open the valve, and af- 

 ter it has passed into the body of the gage, the valve will 

 close the orifice again, suffering, however, the drainings of 

 the funnel to pass along the pendant wire by cohesive at- 

 traction. 



This top, with its funnel and appendages, may be fitted 

 on the body of the gage, like the lid of a common tea can- 

 ister. 



The water being thus introduced into the gage, the 

 method of determining its altitude in inches and decimal 

 parts depends upon the following fundamental statements, 

 in connection with the simple operation of weighing the 

 water in the gage. 



Fundamental Principle. 



A cubic inch of distilled, or rain water, under a 

 medium pressure and temperature weighs 252.525 grains; 

 according to the liatest corrections. Now this number, 

 multiplied by 100, the area of the funnel, in square 

 inches, or that of the top, or bottom of the body part 

 of the gage, gives 252525 grains for the weitjht of 100 

 cubic inches of water. Supposing this quantity of wa- 



