40 Mr James Straton on the Rain-Gauge. 



getable surfaces ;' and I found that, on placing the eye near 

 the level of the tops of the plants, — of growing corn for ex- 

 ample, — beyond which was a dark background, such as a 

 ploughed field or brown heather moor ; that there was a gray 

 mist over the green surface, to the height of eight, ten, and 

 sometimes twelve inches, above which it could not be seen. 



This mist, I inferred, was partly, at least, if not wholly, 

 formed of the particles of water impinged from the 

 vegetable surfaces, when the drops of rain were broken to 

 pieces by the force with which they fell. Hence, I farther 

 inferred that every gauge must necessarily register too much 

 rain if the mouth of the receiver be not raised above the 

 mist or spray which I had seen. From that time I continued 

 to raise all the gauges in the bare soil and gravel-walks, little 

 by little, month after month, and had the satisfaction to find, 

 as I did so, that the excess of water registered, compared 

 with those in the grass lawn, gradually diminished, and that 

 the registration of all the gauges became more and more uni- 

 form with each other, until it was frequently impossible to 

 detect the hundredth part of an inch of difference in the quan- 

 tities registered from the first to the last day of the month. 

 The most frequent exceptions to the rule of uniformity were 

 the largest gauges (18 inches diameter), which generally re- 

 gistered less than the smaller ones ; — an important fact to be 

 kept in view for notice farther on. After they were elevated 

 13, 14, and 15 inches, the earthy matters were not again 

 found in the water, nor adhering to the insides of the re- 

 ceivers, although the outsides of the gauges were generally 

 bespattered from the ground upwards to some distance. The 

 following examples shew the registrations of gauges of va- 

 rious sizes and in different positions, during the two months' 

 greatest quantity of rain which occurred during the experj^ 

 ments : — 





At surface-level in 



Raised 





Grass. 



Gravel. 



15 inches. 





Nov. 1842. 





Oct. 1846. 



1 inch diam 



. 5-33 



5-81 



6-1 



2 



5-26 



5-75 



6-08 



3 



5-18 



5-9 



611 



7 



5-37 







18 





56-8 



4-9 



