230 The Statural Hijlory 



ftands higher or lower in the Glafs, weighs unequally on the air, 

 and gives it a contraction and extenfion, befide what is produced 

 by beat and cold ; he therefore invented a Circular Thermometer, m 

 which the liquor can occaflon no fuch fallacy, it remaining conti- 

 nually of one height,znd moving the whole infirument like a wheel 

 on its axel z . 



36. Amongft other Aerotechnick, here is a Clock lately con- 

 trived by the ingenious John Jones LL. B. and Fellow ofjefws 

 College Oxon: which moves by the air, equally expreffed out of 

 bellows of a cylindrical form, falling into folds in its defcent, 

 much after the manner of Paper Lanterns : Thefe, in place^of 

 drawing up the weights of other Clocks, are only filled with air, 

 admitted into them at a large orifice at the top, which is ftop'd 

 up again as foon as they are full with a hollow [crew, in the head 

 whereof there is fet a (mzllbrafs plate, about the bignefs of a fil- 

 ver half penny, with a hole perforated fcarce fo big as the fmal- 

 left pins head : through this little hole the air is equally expref- 

 fed by weights laid on the top of the bellows, which defcending 

 very flowly, draw a Clcck^line, having a counterpoife at the o- 

 ther end, that turns a pully-wheel, faftened to the arbor or axis 

 of the hand that points to the hour: which device, though not 

 brought to the intended perfeftionof rhe Inventor, that perhaps 

 it may be by the help of a tumbrel or fufie,yet highly deferves men- 

 tioning, there being nothing of this nature that I can find amongft 

 the writers of Mechanicks. 



37. To which may be added, a hopeful improvement of that 

 uncommon Hygrofcope, made of two Veal, or rather Poplar boards, 

 mention'd in our Englifh Phikfopbical Tranfailions % contrived 

 by my ingenious Friend John Toung M. A. of Magdalen Hall, who 

 rationally concluding, that the teeth of the thin piece of brafs 

 placed acrofs the juncture of the two boards, muft needs in its 

 paffage from bearing on one fide of the teeth of the pinion, to the 

 other, upon change of weather, make a ftand as it were in re- 

 Tpefl: of the motion of the axel of the hand ; thinks a pretty ftift 

 firing cut on theunderfide, after the manner of a hwefile, placed 

 flat and not edge-ways, and bearing pretty hard upon an axel ot 

 Copper, may turn the hand upon change of weather in thtpuntlum 

 of reverfion, without any more than a negative reft : which be- 



1 Hiftory of the Royal Society, part. i.Jubfinem. * Philofoph. Trandidl. Numb. 127. 



ing 



