BOOK III. CHAP. VII. 645 



on the different Hate of the atmofphere, before and after a thunder- 

 fhower, confirms this. The air before thefe fhowers fall is ufually 

 clofe, fuffocating, and fometimes even putrid. But afterwards, what 

 cool, refrefhing and delightful fenfations arife from the change which 

 lightning has occalioned, by burning away thofe foul vapours! It is 

 inoie particularly neceffary in climates where the heat of the fun is 

 continually loading the air with corrupt and infalutary exhala- 

 tions. We find therefore the largeft fupply of lightning diftributed to 

 fuch regions which are nioft in want of it; and by the wifdom of the 

 Divine mechanifm, it is likewife provided for the coldeft climates, 

 though but rarely diflinguidied there by any vifible atftion, except at 

 thofe fealons of the year, when by the greateft fummer-heats, which 

 fill their atmofphere with morbid effluvia y it becomes moft ufcful and 

 neceffary to corredl them. 



Dr. Hales therefore well remarks, that fuch a fulphurcous (late of 

 the air is very prejudicial to the inl.abitants of fome countries; and, 

 when of long continuance, makes them iviJJjfor lightning to purify it. 

 So powerful and dudile an agent is doubtlefs applicable to a thoufand 

 good purpofes ; and, in addition to what have already been fpoken of, 

 let me arid, that it fubdues the moft tempeftuous winds, and is to be 

 deemed the chief preventative of that univerfal devaftation fuch winds 

 would always caule within the Tropics, if they were not reftrained by 

 the effects of lightning; and which they never fail to produce, when 

 thofe effeds are for a time fufpended. 



SECT. IX. 



RAIN. 

 The ufual prognoftics of rain in the Southern parts of this iHandare, 

 lightniiig at windward — large towering clouds — fleecy or black, riling 

 in the South-eaft, the South, or South-weft — great heats and faint 

 light fea-breezes for fome weeks or days — immediately before the fall 

 of rain a Wefterly or North-weft wind, for the moft pait gentle: at 

 the fame time heavy clouds, with thunder approaching the land from 

 the Southern points — the tops of the Blue Mountains appearing per- 

 fedlly clear of clouds or mifts — the objedts upon them tolerably diftini5t,. 

 feemmgly much nearer than ufual, or the whole wearing a blucifti caft — 

 great flaftiings of lightning at night in the Southern hemifphere, be- 

 token rain in fixteen or eighteen hours. After three weeks of dry 

 weather, a flight fliock of an earthquake was felt at ten in the even- 

 ing : to this fucceeded a violent rain in the mountains at two in the 

 afternoon the next day. On a change of wind from the South-eaft: 



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