.70 
PLII^y's l^ATUEAL HISTOBY 
[Eook 11. 
duced by the strobe given to the condensed air, and hence 
it is that the fire darts from the chinks of the clouds. It is 
possible also that the vapour, which has risen from the earth, 
being repelled by the stars, may produce thunder, when it is 
pent up in a cloud ; nature restraining the sound whilst the 
vapour is struggling to escape, but when it does escape, the 
sound bursting forth, as is the case with bladders that are 
distended with air. It is possible also that the spirit, what- 
ever it be, may be kindled by friction, when it is so violently 
projected. It is possible that, by the dashing of the two 
clouds, the lightning may flash out, as is the case when two 
stones are struck against each other. But all these things 
appear to be casual. Hence there are thunderbolts which 
produce no effect, and proceed from no immediate actual 
cause ; by these mountains and seas are struck, and no in- 
jury is done. Those which prognosticate future events pro- 
ceed fi*om on high and from stated causes, and they come 
from their peculiar stars \ 
CHAP. 44. — THE OBiaiK OF WINDS. 
Jn like manner I would not deny that winds, or rather 
sudden gusts, are produced by the arid and dry vapours of 
the earth ; that air may also be exhaled from water, which 
can neither be condensed into a mist, nor compressed into a 
cloud ; that it may be also driven forward by the impulse of 
the sun, since by the term ' wind' we mean nothing more than 
a current of air, by whatever means it may be produced^. 
JPor we observe winds to proceed from rivers and bays, and 
from the sea, even when it is tranquil ; while others, which 
are named AUani, rise up from the earth ; when they come 
back from the sea they are named Tropcei, but if they go 
straight on, Apogcei^, 
1 " Prsesertnn ex tribus superioribus planetis, uti dictum est, cap. 18." 
Hardouiu, in Lemaire, i. 322. 
2 Our author's opinion respecting the origin of wmds nearly agrees 
with that of Aristotle ; " nihil ut ahud ventus (ai^e/zos) sit, nisi aer multus 
fluctuans et compressus, qui etiam spiritus {Tzveviia) appellatur;" De 
Meteor. This treatise contains a fiiU account of the phsenomena of 
winds. Seneca also remarks, " Yentus est aer fluens j " Nat. Qusest. hb. 3 
& 6. 
* Aristotle informs us, that the winds termed apogsei {airoyaioi) pro* 
