WIND-MILL IN MECHANICS. 



15 



the surface of the ball; which indicates that 

 they are sufficiently advanced to admit of 

 the separation of the branch from the tree; 

 and this is best done by sawing it ofli at the 

 incision; taking care that the rope, which 

 must have become nearly rotten, is not 

 shaken off by the operation; and then the 

 branch is planted as a young tree. 

 {To he continued.) 



From the same. 

 APPARATUS FOR THE DECOMPOSITION OF 

 THE ALKALIES UNDER NAPHTHA, BY 



GALVANISM. By Mr. W. H. Pepys.— 



Phil. Mag. No. 124. 



To a bottle without a bottom, a glass 

 stopper is accurately ground. The stop- 

 per is perforated through its axis, and a 

 wire that is passed through this perfora- 

 tion, serves to connect a plate of platina 

 lying on the internal surface of the stop- 

 per, with a plate cf copper that serves for 

 a foot to the inverted vessel, and is 

 brought into contact with the positive end 

 of the galvanic trough. 



The alkali, slightly moistened, is placed 

 on the platina plate; the inverted bottle is 

 filled with naphtha, and covered with a 

 wooden cover, through which a platina 

 wire, with a disc of the same metal at the 

 lower end, is allowed to slide. This wire 

 communicates with the negative end of the 

 trough, and the bottom being brought into 

 contact with the alkali, the latter is decom- 

 posed ; the produced metal sometimes 

 floats, but the greatest portion is found im- 

 bedded in the alkali. The gasses evolved 

 during the process, may be collected by a 

 slight variation of the apparatus. 



over the mouth of a third pot, the linseed 

 oil is first strained into it, and kept warm, 

 while the elastic gum is gradually added ; 

 after which tiie oil is strained for use. 



Three parts of English glue, dissolved 

 in water, are added to 24 of very fine 

 leaf lead, and the whole beat together for 

 a-day. The mass is then cut into cakes 

 and dried in the shade. These cakes are 

 dissolved in water, and the metal spread 

 thin with a hair brush upon paper, which 

 after being dried is polished with a stone 

 till it acquires the metallic lustre. The 

 edges are then pasted down on a board 

 and rubbed with the palm of the hand, 

 previously smeared with the above gurra 

 oil, and exposed to the sun. On the twa 

 foUowifig days the operation is repeated,, 

 when it acquires a brass yellow colour. 

 ( To be continued.) 



Thenard^s and Blainvilles Litho^ 

 graphic Ink. — Soap, one-fourth; mutton 

 suet, one-half; yellow wax, one part ;• 

 mastic, in tears, one half, and as much 

 lamp-black as necessary. 



From the same. 

 PROCESS EMPLOYED IN INDIA FOR FALSE 



GILDING AND WHITEWASHING. — Buch- 

 anan's Journey through the Mysore 

 country, fyc. 



The gilding in the palaces at Seringa- 

 patam is false, and prepared from lead 

 only. An oil, called gurra oil, is made 

 by boiling about IS pounds of linseed oil 

 for two hours in a bi-ass pot, to which 

 about 6 pounds of aloes being added, the 

 boiling is continued for four "hours more. 

 Another pot being made hot, 12 pounds 

 of an elastic gum called chunderasu, pre- 

 pared from the milky juices of the ficus 

 glomerata, ficus gonia, and several other 

 trees,) is melted in it. A cloth being tied 



VALUABLE ACID FOR ENGRAVERS, 



M. Deleschamps says the best acid for 

 engraving for every kind of biting, pra- 

 duce a clear and deep line, without eat- 

 ing aioay the sides of the subject, he 

 uses a composition of acetate of silver and 

 hydrate of nitrous ether. The acetate is 

 precipitated into the lower part of the fur- 

 row, where it produces a rapid and ener- 

 getic action, the upper pans of the fur- 

 row are occupied by the nitrous ether and 

 preserved by its presence. — Jour. Frank, 

 Institute. 



From Rees' New CyclopaLMl'iH, (reference to plates not 



given.) 



WIND-MILL IN MECHANICS, 



A machine which is put in motion by 

 the force of the wind. Wind-mills are in 

 general applied to the purpose of grinding; 

 corn, but are occasionally used to give 

 motion to machines for raising water, 

 sawing-mills, or for other purposes. We 

 shall in this article consider the wind-mill 

 as a first mover, or jirinium mobile, 

 which may be applied to many purposes. 



The invention of wind-mills is not of a 

 very remote date. According to some 

 authors, they were first used in France in 

 the sixth century; while others maintain 



