WITH 'ELEVATION* 
811 
gauge is in each case exactly equal to the horizontal distance of 
four dropsj the quantity collected in the two gauges will be 
identicaL The angle of inclination of the rain is seen, therefore, 
to make no difference whatever in the quantity of rain falling 
upon a horizontal surface. To complete the illustration, a third 
rain-gauge (C) has been introduced, of the same size as the 
•others, but tilted at such an angle that the inclined rain-drops 
shall fall perpendicularly to its receiving surface. A gauge in 
this position wdll clearly catch more rain than one whose receiving 
surface is horizontal, but the difference is due to the former 
catching too much, not, as some have hastily assumed, to the 
latter catching too little. By still further increasing the inclina- 
tion of the rain and of the tilted gauge, it is obvious that the 
latter may he made to receive any number of drops, the quantity 
•of rain falling over a given area remaining precisely the same. 
The next theory I would mention comes recommended by no 
less an authority than Prof. Stanley Jevons, as we now know 
him— W. S. Jevons, B.A., of University College, London, as he 
was when he contributed a paper on this subject to the Philo- 
sophical Magazine for December, 1861. 
Mr. Jevons recognises (as others had done before him) the 
undoubted fact that the decrease of rain with elevation is greatest 
in windy weather, and he shows in a very ingenious manner how 
the force of the wind may, without diminishing the true rainfall, 
diminish the quantity collected in a rain-gauge. Mr. Jevons’s 
paper, which had been overlooked by meteorologists in all recent 
controversies on the subject, was unearthed at the last meeting 
■of the British Association by Mr. G. J. Symons, who was under- 
stood, in a general way, to endorse Mr. Jevons*s views. What 
these views are will best appear by an extract from his paper, 
and by a reproduction of one of his diagrams. 
Mr. Jevons, after premising that not only the building upon 
which a rain-gauge may he placed, but even the rain-gauge 
