g6 Mr. Baldwin Latham. 



of latitude as we proceed northward, and i degree for about 

 every 300 feet of elevation, in all probability the region in 

 which the greatest amount of rain would fall in this neighbour- 

 hood, if we had any lofty hills to receive it, would be at an 

 elevation of something less than 3,000 feet, the temperature in 

 this district, at this elevation, corresponding pretty nearly with 

 that of 2,000 feet elevation in the neighbourhood of White- 

 haven. 



A rule for the calculation of rainfall, known as " Hawksley's 

 rule," is that rain increases with the elevation of the ground 

 i\ per cent, for every 100 feet of elevation. This rule appears, 

 from observation, to be applicable to almost every part of the 

 country. There are, however, seasons in which the rainfall 

 increases at a much greater rate than that stated. Taking 

 Mr. Corden's gauge at Wandle-road as the basis of observa- 

 tion, on an average of the past three years, which have been 

 remarkably wet years, the rain gauge established at Botley 

 Hill, which has an elevation of 870-43 feet above sea level, 

 gives an increase in the quantity of rain at the rate of 4*08 per 

 cent, for every 100 feet of elevation. At " Henley," Chelsham, 

 a rain gauge, 607 feet above ordnance datum, showed an 

 increased quantity of rain at the rate of 479 per cent, for each 

 100 feet of elevation above Wandle-road. In the year 1878, 

 the rate of increase of the Botley Hill gauge above the 

 Wandle-road gauge was 2*37 per cent, for every 100 feet of 

 elevation. In the )'ear 1879, the rate of increase was 

 6"9i per cent, for every 100 feet of elevation, and in 1880 

 the rate of increase was 2-63 per cent, for every 100 feet 

 of elevation. It will be observed that the rate of increase 

 at " Henley," Chelsham, for the three years was at a 

 greater rate than at Botley Hill. This is in a great measure 

 due to the physical outline of the district, the Botley 

 Hill gauge being near the escarpment of the North Downs 

 and the Chelsham gauge somewhat inland ; the prevailing 

 winds driving against the abrupt slopes of the North Downs, 

 forces the air upwards into the colder regions, and the greatest 

 rainfall occurs a short distance inland, and not on the verge of 

 the slope of the Down itself. 



Observations made in 1879 tend to show that the ratio 

 increased with the elevation of the stations, for we find that 

 while the rainfall at Botley Hill increased 6'9i per cent, above 

 Wandle-road, it increased 8 per cent, above Nantwich House, 

 which is a higher gauge, while the gauge at Chipstead, at an 

 elevation of 506 feet, increased 7*28 per cent, for every 100 

 feet above Wandle-road ; it increased io'23 per cent, above 

 Nantwich House ; and the gauge at " Henley," Chelsham, 

 increased 5*37 per cent, above Wandle-road, and 6'95 percent. 



