On the characteristic Vropertles of Tannin. 99 



Application nf the maehine to represent the phases of the 

 moony primary planets, and some other phcennmtna in the 

 heavens*. This, I trust, uill he easily understood from 

 the folloiving 



Example. 

 To represent Jupiter and his satellites as they appear 

 through a common telescope, take a piece of paper stained 

 very black, alx)ut three inches square, near the middle of 

 which cut a hole, perfectly circular, to represent the planet, 

 and four small holes, in a line with the centre of the large 

 one, for the satellites ; hut these must be cut out with a 

 small punch, as it is difficult to make a circular hole with a 

 sharp-pointed instrument. After this paper has been p:isted 

 upon a piece of glass, rough ground on one side, draw- 

 three or four lines across the planet with a black lead pencil 

 to imitate the belts. From this simple contrivance the n)a- 

 chine produces a verv beautiful effect. The new moon re- 

 presented this way is a strikiiig resemblance of the real ob- 

 jects in the heavens : cotncts and fixed stars may also be re- 

 presented by the same method. 



The colour of Mars and of the moon, at rising or setting, 

 may be imitated bv covering the screen za with paper stained 

 red, which will reflect a ruddy tint upon the object placed 

 at .r; and this tint may be increased or decreased by only 

 altering the situations of the candles. lam, sir, 



Lvnn, Your most humble servant, 



^"^■'••- '1' '«^'- Ez. Walkkr. 



XVflT. y/ third Series of Experiments on an artifcial Sub- 

 stance which possesse<; the principal characteristic Proper- 

 ties of Tannin ; with some Remarks on Coal. By Chakles 

 IIatchett, Esfj. F.R.S. 



[Concluded irnm p. 7C.] 

 § ^•. 



In mv fir'^t paper I have remarked, that I suspected the 

 tannin of tlie peat moors to have been produced during the 



• Thc'C pli.Tnomena ar<- repicscutcd min-h more exactly by this machiuc, 

 than by any otlnT tli:it 1 fliu arquiiirjtwi with. 



G 2 iuiperfect. 



