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Dr. Wcillis in Philof. Tranfact. N° 231, fays, That 

 'I'hunder and lightning arc lb very like the effctfls of 

 fired gunpowder, that we may reafonably judge they 

 proceed from the like caufe. 



Kow the prinipal ingredients in gunpowder are nitre 

 and fulphur (the admiffion of charcoal being chiefly 

 to keep their parts feparate, for the better kindling of 

 it;) fo that if we fuppofe in the air a convenient 

 tnixture of nitrous asdfulphureous vapours, and thofe 

 by accident to take fire, fuch explofion may well fol- 

 low with noife and light, as in the firing of gun- 

 powder ; and being once kindled, it will run from 

 place to place, as the vapour leads it, like as in a 

 train of gunpowder, with the like effefts. 

 This explofion, if high in the air, and far from us, 

 will do no mifchief, or not confiderable, like a parcel 

 of gunpowder fired in the open air, where nothing is 

 near enough to be hurt by it j but if the explofion be 

 near to us, or amongft us, it may kill men or cattle, 

 tear trees, fire gunpowder, break houfes, or the like, 

 which gunpowder would do in the like circumftances. 

 This nearnefs or farnefs may be eftimated by the dif- 

 tance of the time between feeing the flafh of lightning, 

 and hearing the clap of Thunder ; for though in their 

 generation they be fimultaneous, yet light moving 

 ' fafter than found, they come to us fucceffively. 

 I have obferved, that commonly the noife is about fe- 

 ven or eight feconds after the flafh, but fometlmes it 

 is much Iboner, in a fecond or two, or lefs than that, 

 jufl" afcertheflaflji and then the explofion muft needs 

 be very near us, and even amongft us, and in fuch 



I have more than once prefaged the expeda- 

 tion of mifchief, and it hath proved accordingly. 

 The noife of Thunder is more divdrfified in cloudy 

 weather, becaufe the air is varioufly reverberated from 

 the clouds to us ; but if there are no clouds, the air 

 flows through the open fpaces to our ears, more freely 

 and evenly, and it frequently lightens in fuch weather 

 without Thunder, becaufe the inflammation confift:s 

 only of fulphureous particles, and on the contrary it 

 often thunders in cloudy weather without any light- 

 ning appearing vifibly, becaufe it is intercepted by 



the clouds. 



Rain generally attends Thunder and lightning, either 

 at the fame time, or foon after, and it frequently rains 

 fafter after a clap of Thunder, fo that rain feems to 

 be the effeft of Thunder: > y^^ : -^j 



cafes. 



4-*:- 



4 



As for Thunderbolts ; wHen it "thunder and lightens, 

 there fometimes falls a Thunderbolt. This Thunder- 

 bolt is a moft rapid flame, that darts out of the clouds 

 to the ground, and ftrikes every thing that is in its 

 way, and it is obferved to have, the following peculiar 

 pha^nomena : "" :*:;«s. *»*:.*♦ ."^"'- 



1. That it oftener ftrikes upon high places than low, 

 as upon mountains, towers, fteeples, trees, &c. . 



2. That it fometimes burns peoples clothes without 

 hurting their bodies. ' ^ 



3. That it fometimes breaks their bones, and at the 

 fame time does not hurt their flefh or their garments. 



That it has melted of broken a fword in a fcabbard 

 without hurting the fcabbard ; and, on the contrary, 

 has fometimes burnt the fcabbard all over, and at the 

 fame time done no harm to the fword. 

 • t'rom thefe confiderations we may conclude that a 

 Thunderbolt is an exhalation kindled on a fudden, 

 and is copious enough to be hurried down to us by 

 winds. . i .... 



Thunderbolts are moft commonly darted aflope 

 through the air, and this may be occafioned by the 

 winds, which feldom or never blow downright. And 

 it is probable, that the flame is beaten down by the 

 wind, and reaches the ground before the matter of it 

 is quite fpent. " . ., 



And this may be the reafon that for the moft part 

 they ftrike upon high places ; for, as they fall ob- 

 liquely through the air, they often in their way meet 

 with mountains, towers, &c. and the reafon that the 

 force of their flame is very different, is probably from 

 the difference of the exhalations which form the 

 Thunderbolts, the bodies from which they are col- 



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lefted being fulphureous, bituminou*;, or faline, and 

 from thence it may be, that it fometimes burns gar- 

 ments, at the fame time that itpafies over the bodies 

 without doing them any harm. 



Sometimes it penetrates the foft flelh harmlcfsly, and 

 yet breaks the hard bones, as gold and other metals 

 are diflTolved by aqua-regia and aqua-fortis, and in the 

 mean time the paper fliall not be hurt by them : and 

 for the fame reafon it is, that a fword may be melted 

 in a fcabbard, and yet the fcabbard remain entire ; 

 and fo it would be if they were both laid together in 

 aqua-fortis, becaufe the acute parts of the aqua-fortis 

 do not operate upon the foft matter, the particles of 

 which are branched, as they do upon harder bodies, 

 into the pores of which they infinuate themfelves, and 

 diflblve the contexture. 

 The eS'efts of lightning upon vegetables ire fome- 



. times very great ; it fplits down trees, and there has 

 been many inftances where the bodies of large trees 

 have been torn to pieces, and the chips fcactered to a 

 great diftance, but inftances of this are pretty rare. 

 The killing of branches or parts of trees is very com- 

 mon and fudden •, for when this happens, that part of 

 the tree where the lightning ftrikes, will in a very few 

 hours appear as dead as if it had been fome days fe- 

 vered from the trees. 



THURIFEROUS fignifies bearing or producing 



frankincenfe. 

 THUYA. Tourn. Inft. R. H. 5S6. tab. 358. Lin. 

 . Gen. Plant. 957. [fo called of -S-Jco, to perfume with 

 fmoke, becaufe this plant hath a penetrating fmeil.] 

 The Arbor Vitas, vulgo ; in French, ^r^re de Vie. 



The Characters are, . 

 // has male and female flowers in the fame plant ; the 

 male flowers are produced in an oval katkin* 'The flowers 

 are placed oppq/ite upon the common foot-ftalk^ each flower 

 embracing it with its bafe \ thefe come out of an oval con- 

 cave fcale ; they have no petals^ but have four ftamina 

 which are fcarce difcernible ; their fummits adhere to the 

 bafe of the fcale of the empalement. The female flowers 

 . are colle^ed in a common almofl oval cone, two flowers 

 flanding oppoftte in each fcale j th^ have no petals^ but 

 have a fmall germen, fupporting a flender ftyl\ crowned 

 by a fingle ftigma \ thefe are fucceeded by an oblong oval 

 cone^ opening longitudinally, whofe fcales are almofl equals 

 convex on the ou^tde, and obtufe, each containing an oblong 

 feed with a membranaceous wing, ... .:_ / 

 This genus . of plants is ranged in the riinth fedlon 

 of Linn^us's twenty-firft clafs, which "coritaihs thofe 

 plants which have' male and female flowers on the 

 fame plant, and their ftamina are collefted in one body.- 



The Species are, ■ - ■ ^" . -^ 



1. Thuya (Occidentalis) ftrobilis ^laevibus, fquamis ob- 

 tufis. Hort. Clifi: 449. Thuya with fmooth cones and oh- 

 tufefcales. Thuya Theophrafti. C. B. P. 488. The 



common Arhcr Vit^e, 



2. Thuya (Qrientalis) ftrobilis fquarrofis, fquamis acu- 

 minatis reflexis. Hort. Upfal. 289. Thuya with rugged 

 conesy and acute-pointed reflexed fcales. Thuya ftrobilis 

 uncinatis, fquamis reflexo-acuminatis. Flor. Leyd. 

 Prod. 87. The China Arbor Vit^e. 



The firft fort grows naturally in Canada, Siberia, and 

 other northern countries, but has been long an inha- 

 bitant in the Englifti gardens. In fome of thefe gar- 

 dens, which have not been altered, there are fome of 

 thefe trees which are of a large fize: it has a ftrong 

 ■ woody trunk, which rifes to the height of forty feet or 

 more. The bark, while young, is fmooth, and of a dark 

 brown colour, but, as the trees advance, the bark be- 

 comes cracked and lefs fmooth. The branches are 

 produced irregularly on every fide, ftandingalmoft ho- 

 rizontal, and the young flender flioots frequently hang 

 \downward; thefe branches ftand but thin, and the 

 younger branches only are garniftied with leaves, fo 

 that when the trees are grown large, they make but 

 an indifferent appearance, being fo thinly clothed with 

 leaves. The young branches are flat, and the fmall 

 ' leaves are placed imbricatim over each other like the 

 fcale of fifh ; the flowers are produced from the fide of 

 the vouns branches, pretty near to the foot-ftalk ; the 



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