Mr James Straton on the Rain-Gauge. 37 



(or ignorance) was considerably more important than flatter- 

 ing, and the only alternative in the circumstances was to 

 test the various points in doubt by a series of experiments. 

 This I proceeded with as follows :— I had six sets of gauges 

 prepared and. planted in as many separate localities. Each 

 set consisted of four gauges of the respective diameters of 

 one, two, three, and eighteen inches. It was desirable for prac- 

 tical purposes to determine what is the smallest size of gauge 

 which can be used, consistent with accurate results. This could 

 only be determined by experiment, and hence my reason for 

 planting gauges of one, two, and three inches diameter. A 

 brief summary of the proceedings and conclusions attained 

 will suffice. 



Position. — As Mr Dalmahoy had demonstrated that the 

 quantity of rain increases in its progress downward, I first 

 planted the gauges with the mouths of the receivers level, 

 or nearly so, with the surface of the soil, but I soon found 

 very conflicting results ; I soon found that the quantity of 

 water registered by each gauge was influenced in some way 

 by the state of the surrounding surface — (1.) when it was a 

 smooth well-kept grass lawn, the gauges registered most uni- 

 formly with each other, and the smallest quantity of rain 

 during a given week, month, or quarter ; (2.) when it was 

 soft, pulverised, uncovered earth, there was a greater quan- 

 tity of water in the same period, and the gauges were less 

 uniform with each other in the quantity registered ; and (3.) 

 When the surface was a hard smooth gravel- walk, there was 

 the greatest quantity registered, and the least uniformity in 

 the registrations. Another circumstance which arrested my 

 attention was, that in all the gauges there was a quantity of 

 earthy matter, sand, and clay, settled to the bottom and fre- 

 quently adhering to the in sides of the receivers. Whether 

 this matter was blown in by the wind, or washed in by the 

 rain, became an important question to settle. I therefore 

 continued the experiments through several months, during 

 which the soil was so wet that dust could not be blown by 

 the wind. Still the earth, sand, and clay, found their way 

 into the gauges as before. It also became obvious that the 

 quantity of earth in the gauges at the end of each month 

 bore a proportion (1.) to the quantity of rain which had fallen, 



