T H 



firfl: has a degree of heat under the equirio£lial line, 

 and the othe? a degree of cold in 88 degrees north 



latitude. 



Thcle inftrumcnts, the barometer, hygrometer, and 

 thermometer or Thermofcope, difcover the altera- 

 tions of the air, as to wet or dry, efpecially if it be 

 accompanied with a hygrometer -, and the thermo- 

 meter ihews the condition of the air, as to heat or 



cold. . 



The method prefcribed to be ufcd in keeping the ac- 

 counts or obfervations made on the alterations of 

 thefe inlb-umencs, is that which was ufed by the Hon. 



Samuel Molyneux, Efq; . ,, , 



There muft be a book for the remarks in all the twelve 



months of the year, which are to be made fix times 



every day. At thefe times you mufl obferve, 



I. How the quickfilver riles or falls in the barometer. 



2." What is the alteration of the hygrometer. 



3. How the fpirits in the thermometer rife or fall. 



4. From what point of the compafs the wind blows •, 

 and alfo with what ftrength, according to the neareft 



guefs that can be made. 



n. Whether it rains, fnows, hails, &c. and in what 



quantity. 



Every leaf of the book is to be divided into feveral 

 columns; thcfirftfor the day of the month and the 

 v;eek, the fecond for the number of inches and parts 

 of an inch in the tube of the barometer, where the 

 quickfilver ftands at the time when the obfcrvation 



is made. 



The fecond is to be for marking the degrees, which 



the index of the hygrometer points to at the fame 



time. 



The third is for fhewing the number of inches and 



parts of an inch, where the fpirits Hand in the ther- 

 mometer at the time when the obfervation is made. 

 The fourth is for marking from what point the winds 

 blow, and their ftrength, ■ 



The fifth is for noting the quantity of rain, &c. that 

 falls, and what difpofition the^clouds and aif liave.J 

 Take, for example, the followirigyaccountdf the ad 

 of June, 17^1, which table is infcrted^underneath. - 

 According to this method, a weather book may be 

 kept' of the country' a perfon refides in; and by 

 comparing the motions of the quickfilver and fpirit 

 with the weatTTer, at fuch times^as the obfervations 

 are made, a little praftice will enable a perfon to 

 give a good judgment beforehand what weather will 

 happen. 



The TABLE. 





Friday, June Zy 

 1721. 



- - 



- - — 



Morning at 9. 



€■ - 



F _ - ^ " 



Noon, 



Afternoon at 3. 

 Afternoon at 6. 



I n 



I ' T 



I ' 1 



Evening at 9. 



J - • _ 



Midnight. ^ 



Barometer , 



Inch. Par. 

 29 98 



■ - > 



29 98 



29 98 



+ 



29 98 



1 — 



29 98 



29 '98 



^-1 



_ -I 





280 

 20 



300 

 20 



320 

 5 





b'ygromtier, ^. 

 'With its Di 

 •vijlom and 

 ""arts. 



240 



260 



20 



TFind. 



i ',. 



Weather* 



30 Eafl,brilk Gale. Cloudy. 



— ^ ■ _ ^ »■ — ■ '^ - -- 



'-y 



28Eaft,brifkGale,' 



or ditto. 



1- ., -A 



28 



27 

 28 



28 



Ditto. 



Ditto. 



L 



Ditto, -rl 



■ 



Ditto. 



Ditto. 



V - 



Dittol 



^ , >" - i r , 



Ditto. 



1--' 



--!- 



Ditto. 



' ^ t-i^ 



k . 



A ' 



* -r. 



Mr. Boyle, by placing a thermometer m a cave, which 

 was cut ftrait into the bottom of a cliff, fronting the 

 fea, to the depth of 130 feet, found the fpirit ftood, 

 both in winter and fummer, at a fmall divifion above 

 temperate 5 -the cave had eighty feet depth of earth 



above it, ' ^ 



I, fays Dr. Hales, marked fix thermometers numeri- 

 cally, I, 2, 3, 4, 5, 6. The thermomiCter, number 

 I, which was the fhorteft, I placed with a fouth af- 

 pe6t in the open air 5 the ball of number 2, I fet two 

 inches under ground ; that of number 3, four inches •, 

 number 4,^ eight inches ; number 5, fixteen inches ^ 



and number 6, twenty-four inches : and that the 



THE 



heat of the earth at thofc fcvcral depths may the more 

 accurately be known, it is proper to place near each 

 thermometer aglafs tube, fealed at both ends, of the 

 fame length with the ilcms of the feveral thermome- 

 ters, and with tinged fpirit of wine in them to the 

 fame height as in each correfponding thermometer ; 

 the fcale of degrees of each thermometer being mark- 

 ed on a fiiding ruler, with an index at the back of it, 

 pointing to the correfponding tube. 

 When at any time an obfervation is to be made, bv 

 moving the index to point to the top of the fpirit in 

 that tube, an accurate allowance is hereby made for 

 very diff'erent degrees of heat and cold in the Items 

 cf the thermometers at all depths; by which means 

 the fcale of degrees will ihew truly the degrees of heat 

 in the balls of the thermometers, and confequendy 

 the refpeftive heats of the earth at the feveral depths 

 where they are placed. 



The. ftems of thefe thermometers, which were above 

 the ground, were fenced from weather and injuries, 

 by Iquare wooden tubes. The ground they were 

 placed in, was a brick earth in the midddle of my 

 garden. 



July the 30th he began to keep a regifter of their 

 rife and fall : during the following month of Auguft 

 he obferved, that when the fpirit in the thermometer, 

 number i, (which wasexpofed to the fun) was about 

 noon rifen to 48 degrees, then the fecond thermome- 

 ter v/as 45, the fifth 33, and the fixth 31 ; the third 

 and fourth at intermediate degrees : the fifth and fixth 

 thermometers kept nearly the fame degree of heat, 

 both night and day, till tov/ards the latter end of the 

 month J when, as the days grew Ihorter and cooler, 

 and the nights longer and cooler, they then fell to 25 

 and 27 degrees. 



Now fo confiderable a heat of the fun, at two feet 

 depth under the earth's furface, mud needs have a 

 ftrong influence in raifing the moiilure at that and 

 greater depths, whereby a very great and condnual 

 reek muft always be afcending during the warm fum- 

 mer feafon, by night as well as by day ; for the heat 

 at two feet deep is nearly the fame night and day ; 

 the impulfe of the fun- beams giving the moifturc of 

 the earth a briik undulatino; motion ; which watery 

 particles, when feparated and rarefied by heat, afcend 

 in the form of a vapour \ and the vigour of the warm 

 and confined vapour (fuch as that which is one, tv^o^ 

 or fhree feet deep in the earth) mult be very confi- 

 derable, fo as to penetrate the roots with fome vigour ;. 

 as we may reafonably fuppofe from the vaft force of 

 confined vapour in seolipies, in the digefter of bones, 

 and the engine to raife water by fire. 

 . If plants v/ere not in this manner fupplied with moif- 

 ture, it were impoffible for them to fubfift under the 

 fcorching heat within the tropics, where they have no 

 rain for many months together ; for though the dews 

 are much greater there than in thefe more northern 

 climates, yet, doubtlefs, where the heat fo much ex- 

 ceeds ours, the whole quantity evaporated in a day 

 there, does as far exceed the quantity that falls by 

 night in dew, as the quantity evaporated here in a 

 fummer's day is found to exceed the quantity of dev/ 



k-- ' -. l' 



* — 



which falls in the night. 

 But the dew which falls in a hot fummer feafon cannot 

 poflibly be of any benefit to the roots of trees ; becanfe 

 it is remanded back from the earth by the following 

 day's heat, before fo fmall a quantity of moifture can 

 have foaked to any confiderable depth. '■■^■"' 

 The great benefit therefore of dew in hot weather 

 muft be^ by being plentifully Jm.bibed into vegeta- 

 bles, thereby not only refrefiiing them forthe pre- 

 fent, but alfo furnifiiing them with a frefh fupply of 

 moifl:ure, towards the great expences of the fuccced- 



ing day. 



It is therefore probable, that the roots of trees ana 

 plants are thus, by means of the fun's warmth, cor,- 

 ilantly irrigated with frefh fupplies of m^. iiture ; 

 which, by the fame means," infinuates itfelf with 

 fome vigour into the roots ; for if the moifture of 



the earth were not thus aduated, the roots muft tiien 



receive 



^- 



\ . 



