Observations on the VkcBUomena of Ihe Universe. 285 



and covering it wi^h a thin coating of gum and black ; the part 

 intended for the drawing must be scraped out, and when finished, 

 of course appears white instead of black ; the thicker hues, as in 

 copper, must be cut deeper ; and when the whole is finished 

 the stone is rubbed with linseed oil, which not being able to pe- 

 netrate the coating of gum, only touches the stone where it is 

 scraped away. The gum is then washed off, and the print ob- 

 tained as in 'the other styles of printing. 



The imitations of aqua-tinta are produced by several stones 

 coinciding with each other, and producing a succession of flat 

 tints, as in the drawings 6, 7, 8, 9. Drawings may also be done 

 by mixing ink with chalk, and adding flat tints. 



MR. REDMAN ON LITHOGRAPHY. 



The stone on which the accompanying specimen is executed, 

 was taken from a quarry the property of William James, Esq. qf 

 Warwick, a member of the Society for promoting the Arts, Ma- 

 nufactures, and Commerce. It is situated at Wilmcots, near 

 Stratford-upon-Avon, and the stone may be there procured in any 

 quantity, and of a very large size. I can say from experience 

 (having been some vears in practice as a lithographic printer, 

 in which time I have tried various English stones,) that it is 

 equal to the German stones in texture and hardness, and is ca- 

 pable of receiving any kind of drawings intended for lithographic 

 purposes. 



XLII. Observations on the Phcennmena of the Universe hj a 

 NiiwroNiAN, in Answer to ihe Remarks ofPHiLO-VERiTATis, 

 published in the Philosophical Magazine for last Month. 



To Mr. Tilloch. 



R,R, _ Your correspondent Philo-Veritatis, in his remarks 

 (Phil. Mag. No.2G9) on niv observations relative to the Theory 

 of S/r Richard Phillips, insinuates my having intended to hoax 

 your readers at the expense of truth. I therefore solicit your in- 

 dulgence to insert a few remarks. 



In art. I. page 102, vol. 56. The velocity of the planets in 

 iheir orbits, was by mistake inserted with the density of the 

 gaseous medium, aiid the density of the planets, as will appear 

 by referring to art. 6, page 10'3, i. e. Tlie motions of the planets 

 in superior orbits are quicker than those which are situated 

 nearer the sun. 



Rut had I erred in the three first deductions, as erroneously 



stated by l^hiialis, there would still have been left objections 



^ to 



