Mr Adam's Descrij)tion of a simpU Ram Gage. 



which the requisite divisions or graduation of the scale will be 

 completed, on the supposition that the tube to which it is ap- 

 plied is truly cylindrical, though such tubes are seldom, if ever, 

 found of the required length. 



Thus, let a = (6-8)'x '7854 = 36-31689 D inches = the area 

 of the circular mouth A B of the rain gage. 



b = i^'Oiyx -7854 = 3-36536 square inches 

 = the area of a circular section of the tube b d; 



and c = (564>yx '7854 = -24983 of a square inch 

 = the area of a circular section of the tube c h. 



Then b -{- c = 3-61519 square inches, and y^= 3-61519 

 = 10 inches nearly. 



Therefore 10 inches, 1 inch, and ^^^th of an inch, are made 

 the lengths of the several divisions, marking inches, tenths, and 

 hundredths of an inch deep of rain on the scale i k. Here it 

 may be remarked, that this rain gage has the advantage of 

 giving httle trouble to the observer. But, besides being not 

 very minute in its indications, it has the disadvantage of not 

 measuring the whole of the rain which enters it. For the rain 

 which enters it must fill 1| inch of the small tube de above 

 the stop-cock e^ and also 3 inches of the canaiyc and tube c h, 

 before any part of it can remain on the bottom of the tube bd, 

 or reach .0 on the scale i Jc, that is, before it indicates or niea- 

 sures any portion of the depth of the rain fallen around the rain 

 gage. Now the former source of error, at the stop-cock e, is 

 evidently repeated at every successive observation, and the latter 

 atj'c, in consequence of evaporation, is either wholly or partially 

 repeated at every interval between dry and wet weather. This 

 rain gage, therefore, though sufficiently convenient, has not the 

 advantage of much accuracy in its indications. 



lyvERKESs, 28th January 1832. 



