42 Mr James Straton on the Rain- Gauge. 



happen, however, but only on those rare occasions, once in 

 ten, fifteen, or twenty years perhaps, when intense frost, con- 

 tinued for many days, penetrates deep into the soil, attracts 

 the attention of all, and would of course warn and remind the 

 observer to have his gauge empty. 



Size. — I began experimenting under impressions re- 

 garding the size of gauges similar to those stated by Mr 

 Stevenson, thus : — " But it seems probable that the larger 

 they are made the better, and for ordinary use they could be 

 conveniently enough constructed of from two to four feet 

 diameter." I had no very definite notions, however, as to 

 the why or wherefore a large should be superior in any par- 

 ticular to a small gauge. I close the experiments, convinced 

 that instruments from four or five inches to as many yards in 

 diameter are far, very far inferior in point of accuracy, in our 

 climate, to those of one, two, and three inches wide. The want 

 of uniformity of registration, which I always regarded as proof 

 of want of accuracy also, noticeable from the beginning of 

 the experiments, I was never able to trace to the difference 

 of size of the gauges forming the sets. But when I ulti- 

 mately obtained a very near approach to uniformity by 

 raising them beyond the reach of the spray from the ground, 

 which was so clearly a disturbing cause, I was then surprised 

 to find that, while the small gauges of one, two, and three 

 inches were remarkably uniform with each other in the quan- 

 tities registered, the large gauges of eighteen inches diame- 

 ter were in general considerably below, and in no instance 

 did they exceed the small gauges in the quantity registered. 

 At first I suspected error in the measurement or graduation 

 of the instruments, but on examination found them all equally 

 accurate. The question now came to be, did the small regis- 

 ter too much, or the large gauges too little rain % The very 

 close and habitual uniformity of the small gauges, I could not 

 but regard as presumptive proof, at least, of their accuracy 

 also ; but how the large gauges recorded too little rain was 

 not at all obvious at first sight. The sagacious remark of the 

 keeper of the Buchanness lighthouse, quoted by Mr Stevenson, 

 and verified, as it is, by most of his intelligent co-labourers 

 at the stations round the coast, gave me the right clue to 



