u. 



■;> 



f 



DEW 



la lurtacc: tlnr he filled them wlch pretty moift 

 c^rth, taken otY tht: kirfacc of the ground, and they 

 mcrcalcd in weight by the night's dew 180 grains-, 

 .md decrealed in weight by the evaporat:on ot the day 

 1 ounce + 282 grains. 



lie lavs iikewile, he let thele in other broader pans 

 10 prevent any moifture from the earth (licking to t!ie 

 bottom ot them. He adds, that the moiller the earih 

 is, the more dew falls on it in a night, and more than 

 a double quantity of dew falls on a furface of water 

 than there does on an equal furface of moill earth. 

 The evaporation of a furface of water in nine hours 

 winter's dr>' day, is ^ of an inch : the evaporation 

 of a furface of ice fet in the (hade during a nine hours 



D I A 



Dr. n.ilr^ Tirocoo'U to i-::'-^-'-, in the- ctS- of n l]..n 



> I 1 1 ' I - . 1 



grouiKi wine: 



ne Pive^ in i!>c nnv.!> '_\vprr:pu-:it of Iks 

 book of \'cg-table Statics, ' 





found, from the Hops, coniidcred o:dv u:r ihvcr 

 months, at ^l ,- part or" an inrh c.xch i\A\\ wiiich v.;!! 

 be .,V of an inch : but before- it be allowed 0,2 mdv-; 

 to form tlie furface of the ;:round, which ad Ud t i 

 the .'^- <?ive 7,1 inch 



es 



v.-li:ch is the utmoil thai 



c.\:i 



or 



day, was ^. 



So here are 540 grains more evaporated from the 

 earth every 24 hours in fummer than fall in dew in 

 the night; that is, in 21 days near 2 6 ounces from a 

 circular area of a foot diameter; and circles being as 

 the fquares of their diameters, 10 pounds + 2 ounces 

 will in 21 days be evaporated from the hemifphere of 

 30 inches diameter, wiiich the Sunflower's root occu- 

 pies; which, with the 29 pounds drawn off by the 

 plant in the fame time, makes 39 pounds, that is, 9 

 pounds and -J- out of ever)' cubic foot of earth, the 

 plant's roots occupying more than 4 cubic feet : but 

 this is a much neater de2;ree of drinefs than the fur- 

 face of the earth ever fuflers for 15 mches depth, even | 

 in the drieft feafons in this country/ 

 In a long dry feafon therefore, elpecially within the 

 tropics, we muft hive recourfe, for fufficient moiflure 

 to Keep plants' and trees alive, to the moiil ftrata of 

 earth, which lie, next below that in which the roots 



are.. - ' 



Now moift bodies always communicate of their moif- 

 ture" to more dry adjoining bodies ; but this flow mo- 

 tion of the afcent of moillurc is much accelerated by 

 the fun's heat to confiderable depths in the earth, as 

 is probable, he fays, from the twentieth experiment 

 in the faid book. 



Now 180 grains of dew falling in one night on a cir- 

 cle of a foot diameter = ti^ fquare inches; thefe 



be evaporated from a fuifaceof Hop-'trrour..i in .1 

 year; fo that of 22 inches dep'di of ram, iIktc k- 

 main 15 inches to fupply fprings, v.hich are nv)re o; 

 lefs exhaufl:ed, according; to the drinefs or wetnels 

 the year. 



Hence v.-e find, that 22 inches depth of rain in a 

 year is luflicient for all the purpoles of nature in fu-.h 

 flat countries as that about Teddin^ron near Hamn- 

 ton Court. But in the hill countries, as in Lanca- 

 fhire, there falls 42 inches depth of rain v.atcr, from 

 which, deducting 7 inclies for evaporation, there re- 

 mains 35 inches depth of water for the fprintr.s, be- 

 fides great fupplies from much more plentiful dews 

 than tidl in plain countries ; which valt Itores fecm fo 

 abundantly lufficient to anfwer the great quantity of 

 water, which is conveyed away by tlie fprings and ri- 

 vers from tliofe hills, that we need not have recourfe 

 for fupplies to the great abyfs, whofe furface at high 

 water is furmounted fome hundreds of feet by thofe 

 , vaft hills from whence the loni:,ell and <ireatelt rivers 

 take their rife, 



DIANTHERA. Lin. Gen. Plant. 37. Flor. Virg. 6. 



The Characters are, 



T'bcfower hath a permanent empalement of one leaf ^ '■johich 

 is tubulouSy and cui at the top into Jive eqiiql parts \ the 

 fower is of the grinning kind^ having one petal with a 

 fjjy/'t tube ; the upper lip is reflexed and bifida the lo'wer 

 is divided into three parts^ the middle being the Iroadcfl ; 

 /'/ hath tzvo Jhort fender ftamina adhering to the 

 back of the petals one of thefe hath a twin fummit^ th& 

 other is a little taller. It hath an oblong germcn^ fupport- 

 ■ ing a fender ftyle the length of the famina^ crowned by 

 an obtufe ftigma. The empalement afterward becomes a 

 capfule with two eelL\ opening with two valves^ which 



180 grains being equally fpread on this furface, its j are alternately compreffd at the top and bottom^ and 



depth will be -rf^ part of an inch 



180 



. He adds, 

 113x254 



that he found the dew in a winter night to be the 



part of an mcK '; fo that if we allow 1 5 1 nights for 



the extent of the fummer dew, it will in that time 



T 



Open with an elafiicity^ cafting a fingle flat feed out of each 



cell. 



This genus of plants is ranged in the firfl: feclion of 



Linnseus's fecond clafs, intitled Diandria Monogynia, 



the flower having two flamina and one flyle. . This is 



arife to one inch depth : and reckoning the remaining one of the genera which, by Linnasus's method, is fe- 

 214 nights for the extent of the v/inter's dew, it will parated to a great diftance from their congeners ; for 

 produce 2,39 inches depth, which makes the dew of by all their other charafters they flioiild be joined to 



the whole year amount to 3,39 inches depth. 



And the quantity which evaporated in a fair fum- I are put under his fecond. 



his fourteenth clafs, but having only two flamina, the/' 



-'■ « 



mer's day from the ^me ^furface, being as* 1 ounce 

 282 grains, gives -^ part of an inch depth for eva- 

 poration, which is four times as much as fell' at 

 night: " 



We know but one Species of this genus at prefent. 



- . I 



viz.. 



DiANTHERA {Amertcand) fpicis folitariis alternis. Lin. 

 Sp. 24. Dianthera with folitary alternate f pikes. -^ - T 

 This plant grows naturally in Virginia, and other 

 parts of North America, from whence the feeds have 

 been fcnt to England, where they have fucceeded. 

 This is a low herbaceous plant with a perennial root, 

 which fends out feveral weak ftalks about four inches 



He fays likewife, that he found hy the fame means, 



the evaporation of a winter's day to be nearly the 



fame as in a fummer's day •, for the earth being in 



winter more faturate with 'moifture, that excefs of 



moifture anfwers to the excefTive heat in fummer. ' 



Nic. Cruquius, N'' 381. of the Philofophical Tranf- j . long, garnifhed with roundifh leaves of an aromatic 



aftions, found, that 28 inches depth evaporated in a 

 'whole year from water, i. e. -iV^f an inch .each day at 

 a mean rate : but i\\^ earth in a fum mer's day evapo- 

 rates -^^ of an inch, fo the evaporation of a furface 

 of water is to the evaporadon of a furface of earth in 

 fummer as 10 : 3. . " ' ' ' 



The quantity of rain and dew that falls in a year is 

 at a medium 22 inches. The quantity of the earth's 

 evaporation in a year is at lead 9 + '- inches ; fince 

 that is the rate at which it evaporates in a fummer's 

 day : from which 9 + i, inches are to be deduced 

 3,39 inches for circulating daily dew, there remains 

 6,2 inches ; which 6,2 inches deduced from the quan- 

 tity of rain that falls in a year, there remains at leaft 

 16 inches depth" to' repknini the earth with moif- 

 ture for vegetation, and to fupply the fprings and 



!.' 



nvers. 



odour, ftanding clofe to the ftalks ; they are hairy, 

 and of a dark ^rreen colour; from the fide of the 

 ftalks the flowers are produced in fmall fpikes, placed 

 alternately ; thefe are in ftiape and colour very like 

 thofe of the Clinopodium, but have only two ftamina 

 in each. It flowers the latter end of July, but rarely 

 produces feeds in England* : - ^ • 



H - - ^ r ,fi'^ 



This plant is very difficult to preferve in this coun- 

 try, for although it is hardy enough to live in the open 

 air in England, yet it is very fubjedto rot in winter-, 

 and if it is placed under fhelter, it is apt to drav/ up 

 weak, and foon after decay, fo that at prefent the 

 plants are rare in this country. 

 D I A N T H U S. Lin. Gen. Plant. 500. Caryophyllus. 

 Tourn. Inft. R. H. 329. Clove Gilly Flower, Carna- 

 tion Pink; in French, Oeillet, .. -.. 





- * 



4Y 



The 



-- 



1 



>-« 



\ 



- v 



-*» 



-* * 



■ I 



: 4 



'- - 



i.=v 



