1 



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thanp;rs of heat, &c. to the eye; and tlie latter an 

 inltrumcnt that meafures thofe changes; on which 

 foundation the thermometer fliould be a more accu- 

 rate I'hermofcope. 



This difference the excellent Wolfms taking hold of, 

 defcribes all the thermometers in ufe as Thermolcopes; 

 ihev/ing, that none of them do properly meafure the 

 changes of heat, 6:c. and that none of them do more 

 than indicate the fame. 



Though their different heights, yefterday and to-day, 

 {hew a difference of heat i yet fince they do not dif- 

 cover the ratio of yefterday's heat to to-day's, they 

 are not ftriclly thermometers. 



The Afta Erud. Lipf. propofcs a method of gradu- 

 ating the common thermometers fo, as that the une- 

 qual divifions thereof fhali correfpond to equal de- 

 grees of heat, whereby the ratio of to-day's heat to 

 yefterday's will be meafurcd, and confequcatly the 

 Thermofcope improved into a thermometer. 

 The method is thus : - ' * " 



Take a flehder tube about four palms long, with a 

 ball fattened to the fame ; pour into it fpirit of wine, 

 enough juft to fill the ball when furrounded with ice, 

 and hot a drop oVe'f ; in this ftate feal tlic orifice of 

 the tube hermetically, and provide fix veflTels, each 

 capable of containing a pound of water, and fome- 

 what over-, and in the firft pour eleven ounces of 

 warm water, into the fecond ten ounces, into the 

 third nine, &c. - ■ - . 



This done, immerge the tlrermometer into the fiffi: 

 veflel, and pour into it one ounce of hot water, ob- 

 ferving how high the fpirit rifes in the tube, and noting 

 the point with an unit, then remove the tHernlometer 

 into the fecond veffel, into which are poured tvk> 

 ounces of hot water, and note the place the fpirit rifes 

 to with two ; by thus proceeding till the' whole pound 

 of water is fpent, the inftrument will be found to be 

 divided into twelve parts, denoting fo many terms or 

 degrees of heat; fo that at two, the heat is doubje 

 to that of one ; at three triple, &c. 

 But Wolfius (hews, that though this method is plau- 

 fible, yet it is deceitful, and built upon falfe fuppo- 

 fitions ; for it rakes for granted, we have one degree 

 of heat, by adding one ounce of hoc to eleven of cold 

 water, two degrees by adding twD ounces to ten, &c. 

 It fuppofes that a fingle degree of heat afts on the 



fpirit in the" ball of a fingle force, a double with a 

 double force, &c. ' --- r-..;j..,) 



- - ' . 



Laftly, it fuppofes, that if the effed be produced in 

 the thermometer, by the Tieat* of the ambient air, 

 which is here produced by the hot water, the air has 

 the fame degree of heat with the water. 

 But none of thefe fuppofitions are true ; for as to the 

 firft, allowing the heat of the hot water equally diftri- 

 buted through the cold, one degree of heat will be 

 diftributed through eleven parts, two through ten, 



. three through nine, &c. taking therefore equal bulks 

 . ' of water, e. g. a twelfth part of each, the heat will 



* not be double in the one, triple in another, &c. 



■■T 



■ The firft fuppofition is therefore erroneous,' and fo 

 . is the fecond ; neither is the heat of the hot water 



equally diffufed through the cold ; nor does the heat 

 of the hot water aft uniformly on the fpirit of wine ; 



■ }. e. not with the fame force all the time of its adion. 

 For the third fuppofition ; the heat of the ambient air 



' a6ls not only on the fpirit of wine on the ball, but 

 alfo on that in the tube ; and therefore this, as well 



_ , _ _ , t "V: f^ 



as that, fliould be changed. ' = > ... </« 

 Dr. Hook, in order to adjuft the gradations of a ther- 

 mometer with the greater accuracy, hath contrived 

 and defcribed an inftrument for that purpofe, in his 

 Micrographia, p. 38. 



i k 



The 'u.'ay of filing TljermofcopeSj or fuch cthej- fmall glafs 



tubes, with fpirit of 'loine or water. 



- 



Take the ball of the glafs, and then warm it gently 

 between your hands ; then heat it very well (though 

 gently) before a good fire, turning it round, that it 

 may be ^ equally w^arm ; for, without this caution 



H E 



there will be danger of its breaking : then applying 

 the ball to the Hame of a lamp or candle, burning ic 

 about in it, heat it as hot as you can, without melt- 

 ing the glafs ; and then fpeedily immerfing the open 

 end of the pipe into tlie veffel of liquor that you in- 

 tend to fill it withal, the liquor will rife into it, and 

 fill it near full. 



The reafon of which afce nt of the liquor is, that the 

 air within the ball and the tubes being expelled in 

 great meafure by the heat, or at Icaft rarefied there 

 to a very great degree, the immcrfed open end of the 

 tube keeps oft' the prefTure of the circumambient at- 

 mofphcre on that part of the liquor that the end of 

 the tube covers : but the atmofphere prelTes on all 

 other parts of the liquor in the open veflel ; and, 

 confequently, there being none, or a very fmall 

 quantity of air within the tube to hinder it, forces ic 

 by its weight up into the tube, till it gain an equili- 

 brium with the preflTure or weigllt of the air without. 

 If the tube cannot be filled full enough by this me- 

 thod, the reft may be/upplied by a fmall glafs fun- 

 nel ; thefliank of v/hich muft be drawn out exceed- 

 ing flender, and inferted into the orifice of the tube ; 

 and then, by blowing, 'you may force by your breath 

 the fpirit of wine into the tube, fo as to fill it quite, 

 or to what degree you pleafe. 



Dr. Hook, in his Micrographia, hath an engine for 

 graduating his thermometers, to make them true 

 ftandards of heat and cold. 



The thermometers or Thermofcopes are inftruments 

 of very great ufe to gardeners in the management of 

 ftoves. They fliew by infpeftion the prefcnt condi- 

 tion of the air, and whether it be hot or cold; which 

 day in fummer is the hotteft, and in the winter which 

 is the coldeft, or any part of the day; and from 

 thence many ufeful experiments have and may be 

 made ; viz. how much one fpring exceeds another in 

 coldnefs ; which baths are the hotteft or coldeft ; and, 

 if being held in the hand of a perfon in a fever, or 

 otherwife applied, will nicely fliew the abatement or 

 increafe of a fever. 



The common thermometer which is ufed for hot- 

 houfes, has a long tube of about two feet in length, 

 and is about the eighth part of an inch diameter ; and 

 in this it is remarked, that the air is cold for the 

 plants when the fpirit rifes to fifteen inches ; that it 

 is temperate at fixteen inches and a half; that it is 

 warm when it rifes to eighteen inches ; and this is 

 the ftandard for Pine apple heat. It is marked for 

 hot air at twenty inches, and fultry hot at twenty- 

 one and a half; but in the common thermometers, 

 thefe degrees are differently marked ; this temperate 

 : air is about our warm, this warm air our hot, and our 

 hot air is about. the fame as the fultry. 

 Thefe thermometers are marked with fome of the 

 names of the moft remarkable plants which are pieferv- 

 ed in the hot-houfes; but as the number of thefe plants 

 has been greatly increased in England of late years, I 

 'have direded fome thermometers to be made with a 

 fcale divided into degrees^ and with three different 

 points of heat marked in claffes, which correfpond 

 with thefe thermometers ; and under each clafs I have 

 drawn up lifts of the feveral plants, ranged according 

 to the degrees of heat in which they are found to fuc- 

 ceed ; whereby the culture of them is made eafy to 

 perfons of fmall flcill.*— "' 



i * 



.■^-»-->' -J -^ - 



By this means every gardener may know when it is 

 proper to apply his heat in Its full force, and what 

 degree of heat ought to be ufed for the welfare of any 

 plant from any part of the world. 

 Mr. Patrick has fixed his thermometer to a fcale of 

 ninety degrees, which are numbered from the top 

 downwards, and alfo a moveable index fitted to it. 

 The defign of this is to fliew how the heat or cold is 

 changed, from the time it was laft looked upon, ac- 

 cording to the different degrees of heat and cold in 

 all latitudes ; as by the trial of two thermometers 

 that have been regulated abroad^ the one by Dr. 

 Halley, in his late fouthern voyage, and the other by 

 Capt. Johnfon, in his voyage to Greenland. ■ The 



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