1824.] Mr. Chilton on an improved Rain Gauge. 113 



tin or sheet iron painted or japanned, but copper is more dura- 

 We The area ofthe funnel, and that of the top of the body 

 part ore the only parts that need attention in the construction 

 These ou ant to be made tolerably exact. A strong hoop should 

 L fixed around them on the outside to preserve their figure ^ru . 

 In every operation of weighing, the weight of the gauge, 



J^teneTinTe inside, ^^^^^Sh^i 

 the remainder is the corrected weight of the water with which 



fc jST«=M^. ** or h- wa£ Wng in the 



eaucre it is not necessary to melt its contents into water, as the 

 fhanges effected by temperature and pressure make no differ- 



^« afSak. and weights mav be dispensed with, by sub- 

 stitetin" a steelyard, so constructed that the movable weight on 

 S^JaffSSSt. by its position, not the weight, Wi the 

 inches and° decimal parts of its corresponding altitude, without 

 reference to the tables, and without calculation. _ 



T^ advantages of this method of finding the quantity of ram 

 in Search* of altitude, will be appreciated by adverting to 

 the circumstance of our having a tangible quantity, as» 

 ing ffuide to that which is nearly imperceptible ^nty hve 

 grains and a half, a sensible qnantity in a good ba lance point- 

 fno- out the difficultly v sib e division of the ToW tn P alt 0I an 

 bfb^SuTpose the problem reversed ; that th ; cubical content, 

 ofthe water, or its weight, were ^ved Jiom the oteervea 

 iltitude The chances of error would all be against the accuiacy 

 o fsuch a determination. The difficulties of the task mdepen 

 dently of the aforementioned causes ot variation, would evidently 



be insurmountable. . . , , fmirtppn 



I had a gauge constructed on this principle, twelve or fourteen 

 years a-o for my friend Dr. Akerly, who informs me that t 

 an wered'theend y extremely well. This testimony in ^s ^vour 

 is not among the least of those considerations that have induced 

 me to make it more generally known. 



Fig. I. 



New Series, vol. v in. 



