124 farmers' and mechanics' journal. 



It will sometimes happen, that a picture, wheie the surface is 

 smooth, will look too bright and glaring, which is both disagreea- 

 ble to the eye, and injurious to the effect of the picture : to reme- 

 dy this defect, after the varnish is quite dry, say in ten or fifteen 

 days, sponge the picture all over with pure rain water, for about 

 one or two minutes ; and having squeezed the sponge, and made 

 the picture as dry as the sponge will leave it, pass, lightly, a clean 

 silk handkerchief over it with great rapidity, until it become per- 

 fectly dry ; when a clear, steady, lucid, appearance, will pervade 

 the whole picture. Breathing occasionally on the picture to damp 

 it, will assist the operation, while chafing it with the handkerchief. 

 Yours, very respectfully, Joshua Shaw. 



Philadelphia, July 12<A, 1827. 



This is the last number that has iappeared in the Franklin Jour- 

 nal. Should any others appear they shall be continued in this. 



WHEEL CARRIAGES. 



Gentlemen, — I have read with considerable interest the papers 

 of E. Vialls and other correspondents, on the subject of the line of 

 draught most proper for wheel-carriages. I remember to have 

 heard the same subject extremely well treated by the late Mr. 

 Walker, in the course of lectures which he used to deliver in dif- 

 ferent parts of England, on Experimental Philosophy ; and if a 

 ifew extracts from my notes of the same, can be of any service to- 

 wards the elucidation of the matter, they are very much at the 

 service of your readers. E. Knox. 



Bristol, f^ng. 



A horse, considered as a machine, is admirably constructed for 

 draught or sustaining weight. His limbs form an assemblage of 

 levers, which it would require a volume to point out. Attend, 

 however, particularly to the formation of his shoulders : at the 

 place where the neck rises from the chest of the horse, the shoul- 

 der-blades forn) the resting-place of his collar or harness into a 

 slope or inclination, and as this slope or inclination forms an angle 

 with a perpendicular to the horizon of about 14 or 15 degrees, it 

 is clear the line of his draught should form the same angle with 

 the horizon — Why ? Because the horse will then pull perpendicu- 

 larly to the shape of his shoulder, and all parts of the shoulder will 

 be equally pressed by the collar. 



The horse, besides, considered mechanically as a lever, has in 

 this inclined draught a manifest advantage over all obstacles op- 

 posed to it in comparison with an horizontal draught ; its power is 

 in fact doubled. 



We are entitled, therefore, to conclude, that single horse-carts 

 ■^re preferable to teams, and that four single-horse carts will draw 

 more than when yoked to one cart. The reason — Because, in the 



