164 
From July the fth, 1766, to July the /th ? 1767, there fell into a 
rain-guage fixed 
Below the top 
Upon the top 
Upon Westmin 
of a house. 
of a house. 
ster Abbey. 
Inches. 
Inches. 
Inches. 
1766 , From the 7 th of July to the end 
3,591 
3,210 
2,311 
August ..... 
0,558 
0,479 
| 0,508 
September . . . 
0,421 
0,344 
October .... 
2,364 
2,661 
1,416 
November . . . 
1,079 
0,842 
0,632 
December . . . 
1,612 
1,258 
0,994 
January .... 
2,071 
1,455 
1,035 
February .... 
2,864 
2,494 
1,335 
March ..... 
1,807 
1,303 
0,587 
April ...... 
1,437 
1,213 
0,994 
May ...... 
2,432 
1,745 
1,142 
June ...... 
L 977 
1,426 
\ 1,145 
From the 1 st of July to the 7 th . . . 
0,395 
0,309 
J 
22,608 
18,139 
12,099 
By this table it appears, that there fell below the top of a house above 
a fifth part more rain than what fell in the same space above the top of the 
same house, and that there fell upon Westminster Abbey not much above one 
half of what was found to fall in the same space below the top of the houses. 
What may be the cause of this extraordinary difference, adds Dr. Heberden, 
has not yet been discovered; but it may be useful to give notice of it, in 
order to prevent that error, which would frequently be committed in com¬ 
paring the rain of two places without attending to this circumstance. 
It is probable, that some hitherto unknown property of electricity is con¬ 
cerned in this phenomenon. This power has undoubtedly a great share in 
the descent of rain, which hardly ever happens, if the air and electrical appa¬ 
ratus be sufficiently dry r without manifest signs of electricity in the air. 
Hence it is, that in Lima, where there is no rain, they never have any light - 
ning or thunder ; and that, as M. Tournefort was assured, it never rains in 
the Levant but in winter, and that this is the only season in which any 
thunder is heard j. If this appearance therefore could be accounted for, it 
would probably help us to some more satisfactory causes of the suspension of 
the clouds, and of the descent of rain. 
"See the English translation of the Voyage of Don George Juan and Don Antonio de Ulloa, to 
South America, Vol. III. Book I. chap. 6 . p. 69 and 79 . 
f Voyage du Levant, Let. x. p. 423. 
