150 MicrROGRAPHIA, : 
fented inthe 4.Figureof the 15. Scheme. Or,if youintend tomake uf of 
many. of thefe {mall Beards join'd together; you may have'a dmall long 
Cafe of Ivory, whofe fides are turn’d of Bafket-work, full of holes, which 
may be ferew'd on tothe underfide of a broad Plate of Ivory,on the other 
fide of which is tobe made the divided Ring or Circle, to which divifie 
ons the pointing of the Hand or Index, which is moved by the conjoin‘d 
Beard, may fhew all the AG@wute variations of the Air. nod) niitem 
‘There may be multitudes of other ways for contriving this fmall Infttu- 
ment, fo'as to produce thisieffett, which any one may, according to his 
peculiar ufe, and thé exigency of his prefent occafion, eafily enough con- 
trive andtake, on which I fhall not therefore infift.. The whole manner of 
making any one of them is thus: Having your Box or frame AA:BB, fitly 
adapted. for the free paflage of the Air through it,in the midft of the bot- 
-tomB BB, you mufthave a very {mall hole C, into which the lower end of 
the Beard.is to be fixd,the upper end of which Beard 2 4.isto pas through 
a {mall hole of a Plate, or top A A, if you make ufe onely of a fingle one, 
and onthe top ofit ¢, is to be fix'd a fmall and very light Index fg, made 
of a very thin {liver ofa Reed.or, Cane 5 butif you tuake ufe of twoor 
moreBeards, they -muft be fix’d and bound together, either with — 
| fine piece of Silk, or with avery {mall touch of hard Wax, or Glew, which 
is better,and the Index fg, isto be fix'd on the top of the fecond,third, 
or fourth in the fame manner as onthe fingle one. | otf i 
. Now, becaufe that-in every of thefe contrivances, the Index fg, will 
with fome temperatures of Air, move two, three, or more times round, 
which without fome other contrivance then this,will be difficult to diftin- 
guifh,therefore I thought of this Expedient ; The Index or Hand f g,be- 
Ing) taisd a pretty way above.the furface of the Plate AA, fix in ata 
little diftance from the middle of ita {mall Pin 4, foasalmoft to touch 
the furface of the Plate A A, and then in any convenient place of the 
furface of the Plate,fix a {mall Pin, on which put ona {mall piece of Paper, 
or thin Paft-board; Vellom, or Parchment, made of a convenient .cize, 
and fhap‘d in the manner of that in the Figure exprefs'd by 2k, fo 
that having a convenient number of teeth every turn or return of the 
Pin 4, may move this {mall indented Circle, a tooth forward or back- 
wards, by which means the teeth of the Circle, being mark’d,,it will be 
thereby very eafieto know certainly, how much variation any change 
of weather will make upon the {mall wreath’d body. In the erie 
this Secundary Circle of Vellom, or the like, great care is to be had, that _ 
it be made exceeding light, and to move very eafily, for otherwile 
variation will {poil the whole operation. The Box may bemad ae 
Silyer, Iron, or any other fubftance, if care be taken.to make i “ns 
enough, to let the Air have a fufficiently free accefs to the Beard. - Th 
Index alfo may be various ways contrived, fo as to thew both the number 
of the revolutions it makes, and the AGmute divifions of each revolution. 
have made feyeral trials and Inftruments for difcovering, the drinefs 
and moifture of the Air with this little wreath’d body,and find it to vary 
exceeding fenfibly with the leaft change in the conftitution of the Asses 
