£04 Memo, on the subject of Rain Gauges, [no, %, new series, 



all, a heavy fall of rain, the receiving vessel must be a large one, 

 if the Funnel diameter is 12 inches. No ordinary bottle (which is 

 the cleanest and best receptacle) will do, and the consequence is a 

 chatty is used, which is porous, easily broken and awkward to pour 

 from into a narrow cylinder. 



The second objection is, that the Register is not intelligible 

 generally to those who keep it, and the orders of the Board that 

 the Registers are to be sent to them to reduce " Measures," " Inches'' 

 and " Tenths," give the idea, that the inches and tenths, are inches 

 and tenths fall of ram which is not the case. It will also be seen 

 that the reductions are tedious when they come to extend over se- 

 veral Reports. Every " measure" has to be multiplied by 5, every 

 inch by -0625, and every " tenth" by " -00625. 



Now I venture to suggest a form of Rain Gauge which will re- 

 gister accurately to 100th of an inch fall of rain, and which will be 

 free from every objection urged against the present one. The Fun- 

 nel is 4*97 inches in diameter, and its area is therefore, 17'33 

 square inches, therefore a fall of rain of one inch, is 17*33 cubic 

 inches in the reservoir, which is simply a common quart bottle. 

 The rain water is poured out of the bottle into a little tin vessel 

 holding one fluid ounce, and each of these full denotes that T V of 

 an inch of rain has fallen. A stick notched to a 10th of the depth 

 of the little cylinder, will show how many tenths of water there are 

 in the said cylinder, and each of these is equivalent to of an 

 inch of rain, though for country work, a 10th of an inch (each cylin- 

 der full being T \ of an inch) may be sufficient. 



The diameter of the Funnel, is theoretically, 4-697 inches ; but 

 in practice, 4 65 is found sufficient. This is a little smaller than 

 the theoretical diameter, because it is impossible to expect Native 

 workmen to bend the mouth of a tin funnel, to a true cylinder. 



The tin funnel is much cheaper than a copper one. 



A wooden Gauge might be sent from Madras to each Cutcherry, 

 to which the funnel might be fitted. 



The quart bottle is more convenient than a chatty or earthern 

 ware pot, and is quite large enough to suit any fall of rain ' in the 

 Carnatic. It will run over if the fall is above 3 J inches, but this 



