694 



FARMERS' REGISTER 



[No. 11 



a total of 3,860,000 tons consumed in the making 

 of iron. Accnnlinfr ro Mr. Kennedy, the quanti- 

 ty of coal cousiiiueil in the colton nianiifaclure, in 

 1817. was upwards ol" 590,000 tons, and the man- 

 ufacture has since more than doubled; so lliai, al- 

 Jowini'; for irreafer economy, we may fairly esii- 

 niaie ihe consunipiion of coal in ihe cotton trade 

 at 800,000 tons a year. Its consunipiion in the 

 woollen, linen, and silk trades cannot be less tlian 

 500,000 Ions. Tiie sniehinp; of conper ores of 

 Cornwall consume annually about 250.000 or 300,- 

 000 tov'.s; and it is supposed thai the brass and 

 copper manufactures require nearly as much. In 

 the salt works of Cheshire, Worcestershire, &c. 

 the consunipiion is prol);dt!y not under, if it do not 

 exceetl, 300,000 Ions. Tlie consumption in lime 

 works may, it ia believed, be esiimated at 500,000 

 tons. It would appear, ihcreiiire, that the total 

 annual consumption of coal in Great Britain may 

 be moderately esiimated as follows: — 



Tons. 

 Domestic consurription, and smaller 



manufactures - - - - 15.000,000 

 Production of iiijr and bar iron - S.ScO.OOO 



Cotlon manufacture - - - 800.000 



Woollen, linen, silk, &c. - - 600,000 



Copper smelling, brass manufactures, S;c. 450,000 

 Salt works - - . . 300,000 



Lime-works _ - _ _ 500,000 



Exporis to Ireland _ . _ 

 Ditto to colonies and foreign parts 



21.350,000 

 '750,000 

 600,000 



Total 22,700.000 

 If we suppose that the above sum of 22,700,000 

 tons cost ihe consumer, on an average, 7s. a ton. it 

 will be wonh, in all £7,955,000 a year!— ii'CuZ- 

 locWs account of ihe British Empire. 



h'lom SilUman-s Journal. 



Davenport's recent experitiiekts in 

 electuo-magnetic biachikery. 



(Copy of a letter from Mr. Davenport.) 



To Professor S'lUman. 



Dear Sir — Having lately made a number of 

 applications of the power ol' large galvantic mag- 

 nets in propelling machinery, (being independent 

 of the larjie machine now consiruciing by ihe as- 

 sociaiion,*) I have thought proper to slate to you 

 the results, believing they would not be uninter- 

 esting 10 you. 



I have constructed a machine, with two revolv- 

 ing magnets, two feet in lengih, niade of iron 

 three and a half inches in diameter, and weigh- 

 ing, after being wound with six coils of No. 10 

 copper wire, one hundred pounds each. Three 



* The machine alluded to in the above letter, as 

 now being constructed for the Elsctro-JMaguetic asso- 

 ciation, by Messrs. Davenport & Cook, is'iiearly com- 

 pleted, and is expected to be of about two tons power. 

 It is formed bj"- a combination of small ma<;nets, 

 weighing about four pounds each, and three and a half 

 inches between the poles. These magnets are placed, 

 two hundred and thirty four in nnmiier, on an iron 

 shaft six feet in length, and a corresponding number in 

 a circle as stationary magnets. 



stationary magnets of two feet diameter, were 

 placed around the periphery making six poles, and 

 weifjhing one hundred pounds each. 



Willi this machine I produceil one hundred 

 revoluiions per minute, wilh six square it^et of 

 sl'.eel zinc exposed to action, surrounded with thin 

 sheet copper. 



I then displaced the stationary maiinets, and 

 subsiiuiled one ma<rner Uiree inches in diameter, 

 forming a semicircle, wiih the poles direcily oppo- 

 site each other, ami weighing about one hundred 

 pounds. With this niaunet I produced one hun- 

 dred and liliy revolutions ^pe^ minute, using the 

 smie quan'ity of zinc surfiice. Wilh one revolv- 

 ing maiinet 8 produced one hundred and seventy- 

 five revolutions per minute, with foursquare feet 

 of sheet zinc. 1 next conslrncted a /te/Zoio mag- 

 net of Iwo feet in lengih and four inches in diame- 

 ter, made of boiler iron, five-sixteenths of an inch 

 in thickness, wilh four coils of copper wire, with 

 which I succeeded in getting one hundred revolu- 

 tions per minule. A hollow magnet was then 

 constructed of thin sheet iron, of the thickness of 

 common siove-pipe iron, which revolved one iiun- 

 dred and fifty limes per minule. Bollnw magnets 

 I think may be used to great advantage where 

 weiffht is an objection: but in my experiments I 

 generally make use of solid iron. 



I also constructed a machine with simply two 

 mairnels formed of two inch round iron, of fifteen 

 inches in length, of the slirrup form. The dis- 

 tance between the cenlres of tlie poles is five in- 

 ches, and the magnet revolves lour hundred and 

 fil'ly times per minute, with two square li^et of 

 zinc. The siationary magnets being placed wilh 

 the poles pointing upwards, and ihe poles of the 

 revoivins magnet poinlins downwards, the shaft 

 to which the revolving magnet is attached passes 

 through ils centre, and rests on the cenire of 

 ihe siiilionary maffnet. Two of these machines 

 (wciidiinji in all fitly pounds) I have attached to 

 small drilling-works, which I find produce suffi- 

 cient power to do all my driiiing of iron and steel, 

 to the size of or;e-!ourih of an inch dianieler. 



I have adopted this form on the third machine 

 which I have recently put in operation. The 

 magnels are formed of two and ihree-lburth inch 

 iron with the centres of their poles nine inches 

 ai)ari and weiirhingSO lbs. each, with ihis I pro- 

 duced three hundred revolutions per minule, and 

 have successfiilly attached it to turning hard wood 

 of three inches diameter. I find the power in- 

 creases in (idl pro[ioi;tion to the increase of weight 

 and without increasing in proportion the size of 

 the battery. Tlie wire must be increased in size 

 in proporiion to the size of the iron used, and con- 

 sequently the difiiiculiy attending long wires will 

 always be avoided. 



I find no difficulty in using ray machine twelve 

 hours in succession, without changing batteries or 

 agita'.inof the solution. 



I am erecting conveniences to test the powers 

 of each ma.'rnet as ihey are increased in weight 

 and size, and think 1 shall be able in season lor 

 the April number of your Journal to give the ex- 

 act increase of power in proportion to weight, ol 

 magnets weighing frcm ten pounds to several 

 tons. 



I have a'so made some very satisfactory trials, 

 while niakir.si: my machines, respeciing ihe ex- 

 pense for the consumption of zinc and acids, and 



