168 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[April, 



^ 





Z:. 



• >.A *^ ti,p infl.ipnce of the electric current is decomposed in a quantity 

 jected to tbe '"''"f""/' ,; „ua„tity of electricitv which passes through it, 

 exactly proporUona e «; ^^ q^^j'^'y;,, ,„„aitions and circumstances under 

 l^hT^rv^'e Placed andThis is generally true of all electrolytic bodies. 

 We reJret ilLt while on tlm subject we cannot give the interesting summary 

 r lie „t miTp 209 of Mr. Noad's work. 



n , ,e s nbkct of the voltaic pile it is well known that Faraday has given 

 hisslort.o the chemical theory, and the evidence adduced by him has 



ntuV^nntiihutcd to its reception in this country. 

 ^" The source of the electricitv of the voltaic- pile was made by Dr. Faraday 

 the subiect of the 8th, 16th, and 17th series of h,s Experimental Researches. 

 Ilavinc succeeded in producing electricity guite independent Fig. 8. 



of contact, a plate of zinc (Fig. 8) was cleaned and hen 

 in the middle to a right angle; a piece of platinum, about 

 three inches long and half an inch wide, i was fastened to 

 a platinum wire, and the latter bent as in the figure. These I r-±^x 

 two pieces of metal were arranged as shown in the sketch ; ji^ J ^ 

 at xa. piece of folded bibulous paper, moistened m a solu- <-! ^=> 

 tion of iodide of potassium, was placed on the zinc, and 

 ^^•as pressed upon by the end of the platinum wire ; when, 

 under these circumstances, the plates were dipped in the 

 diluted nitric and sulphuric acids, or even in solution of 

 caustic potash, contained in the vessel c, there was an im- 

 mediate effect at .r, the iodide being deconiposed and iodide 

 aopearing at the anode, that is, against the end of the pla- 

 finnm wire As long as the lower ends of the plates remained in the acid, 

 Z electric current proceeded, and the decomposition proceeded at ^. On 

 removing the end of the wire from place to place on the paper, the eflfect 

 "as evidentlv very powerful ; and on placing a piece of turmeric paper be- 

 Tween the white paper and the zinc, both papers being moistened with a so- 

 lution of iodide of potassium, alkali was evolved at the cathode against the 

 zinc in proportion to the evolution of lodme at the anode; the galvanometer 

 also showed the passage of an electrical current; and we have thus a simple 

 circle of the same construction and action as those described in the last 

 lecture, except in the absence of metallic contact. 



"The mutual dependence and state of the chemical athmties of two dis- 

 tant portions of acting fluids, is well shown in the following experiments. 

 Let P (Fig. 9) be a plate of platinum, 

 Z a plate of amalgamated zinc, and y a 

 drop of dilute sulphuric acid ; no sen- 

 sible chemical action takes place till 

 the points P Z are connected by some 

 body capable of conducting electricity: 

 then a current passes ; and as it circu- 

 lates through the fluid at y, decomposi- 

 tion ensues. 



" In Fig. 10, a drop of solution of 

 iodide of potassium is substituted, at x, 

 for the acid : the same set of eftects 

 occur ; but the electric current is in 

 the opposite direction, as shown by the 



arrows." , ^ , ^ ■ -i / 



He has also shown that electrolvtes can conduct a current of electricity of 

 an intensity too low to decompose them, and has given his support to the che- 

 mical theory of galvanism. We wish much we could enter at length into 

 Faraday's views with regard to the magnetism of metals. He considers all 

 metals'as magnetic, in the same manner as iron, though not at ordinary tem- 

 peratures or 'under ordinary circumstances. His opinion is that there is a 

 certain temperature for each metal (as in the case of iron where it is well 

 known) beneath which it is magnetic, and above which temperature it is 

 devoid of magnetic power. He thinks too that there is a relation between 

 such point of temperature and the magnetic intensity, which the body can 

 acquire when reduced beneath that point. 



Upon the subject of magnetism, Dr. Faraday, reasoning on the relative 

 motions of tbe needle and electrified wire, "Conceived that the pole of a 

 magnet ought to revolve about the conductor, and the conductor about the 

 pole of a magnet, and by the fnllowing ingenious apparatus he succeded in 

 proving this to he the case : — Into the centre of tbe 

 bottom of a cup, as in the vertical section, Fig. 11, a 

 copper wire c, D, was inserted, a cylindrical magnet 

 71, s, was attached by a thread to the copper wire c, 

 and the cup was nearly filled with mercury, so that 

 only the north pole of the magnet projected. A con- 

 ductor, a, b, was then fixed in the mercury, perpen- 

 dicularly over c. On connecting the conducting 

 wires with the opposite ends of the battery, a current 

 was transmitted from one wire, through tbe mercury 

 to the other. If the positive current descended, tbe 

 north pole of this magnet immediately began to ro- 

 tate round the wire, a. b, passing from east through 

 the soutli to west, i.e., in the direction of the hands 

 of a watch ; hiit if the current ascended, the line of 

 rotation was reversed. Conversely, a magnet was 

 fixed in a vessel of mercury, and the conducting wire 

 hung from a hook above it, the end just dipping into the fluid ; the electric 

 current being then transmitted through the moveabl a'jnductor,Faradayfound 



Fig. 9. 



Fig. 10. 



S 



Fig. U. 



Fig. 12. 



that the free extremity instantly began to revolve round the 

 pole of the magnet, in a direction similar to the last. ^^ A 

 good contrivance for exhibiting this is shown in Fig. 12." 



To conclude — 



" The direction of the current of electricity which is ex- 

 cited in a metal when moving in the neighbourhood of a 

 magnet is shown to depend upon its relation to the magnetic 

 curves. Faraday, with his usual happy method of illustra- 

 tion, has given us this popular expression of it. Let A B, 

 Fig. 13, represent a cylinder magnet, A being the marked, 

 and B tbe unmarked 'pole; let P N, he a silver knife-blade, 

 resting across the magnet with its edge upwards, and with 

 its marked or notched side towards the pole A ; then in 

 whatever direction or position this knife be moved, edge 

 foremost, either about the marked or unmarked pole, the 

 current of electricity produced will be from P to N, provided 

 the intersecting curves proceeding from A, abut upon the notched surface on 



Fig. 13. 



the knife, and those from B 

 upon the un-notched side ; or 

 if the knife be moved with its 

 back foremost, the current will 

 be from N to P, in every pos- 

 sible position and direction, 

 provided the intersected curves 

 abut on the same surfaces as 

 before. A little model is easily 

 constructed, by using a cylin- 

 der of wood for a magnet, a 

 flat piece for the blade, and a 

 piece of thread connecting one 

 end of the cylinder with the other, and passing through a hole in the blade 

 for the magnetic curves ; this readily gives the result of any possible direc- 

 tion." 



We must observe that Dr. Faraday has given to the world a laborious 

 work, entitled Experimental Researches on Electricity, embodying the results 

 of the papers he published from 1831 to 1810, and he is a constant contri- 

 butor to the Philosophical Transactions of the Royal Society, and to the 

 scientific periodicals. 



DESIGNS. 



Original Geometrical Diaper Designs. By D. R. Hay, Decorative 

 Painter to tbe Queen. London : Bogue. Part I. 



Those who take up this work must closely attend to its title, for it 

 purports to give no more than what it does give, geometrical diaper 

 designs. Those therefore who may fancy that they are to have ex- 

 amples of general decoration will be disappointed, and have only 

 themselves to blame. The restriction of the work to diaper designs 

 shows the importance which is beginning to be attached to decoration 

 in this country, a movement which has been in a great degree for- 

 warded by Mr. Hay himself, and before which movement it would 

 have been quite hopeless to have expected a work on a single branch 

 of decoration, and still more hopeless to have brought it out. As it 

 is there are many who will look at Mr. Hay's lines and circles, and 

 marvel what there can be in them, or why people should ever buy 

 such worthless trifles. Design however in no department can be sately 

 neglected in a commercial country, and still less in this country, where 

 we have suffered and are vet suffering in a high degree the conse- 

 quences of our disregard for art. The raeclianical genius ef our 

 countrvmen, their unequalled manual skill avail iis nothing, the mo- 

 ment any degree of taste is required in the production of a marketable 

 article, and we have as it were abandoned many of the most lucrative 

 br.inches of manufacture to foreigners who labour with our own ma- 

 chinery. The foreign trade of France in manufactured goods entirely 

 consists of articles of taste, fine silks, fine cottons, jewellery, orna- 

 menls, stained paper and decorated articles of every description, ol 

 which they have the monopoly in foreign markets. So it is witli the 

 Swiss the Prussians, the Belgians, and other competitors, they exist 

 mainly bv our ignorance and' our neglect, at the same time that tUey 

 absolutelV imnort largely into this country. The consequent loss is 

 not to be reckoned bv" thousands or hundreds of thousands, but by 

 millions, which, had we the requisite instruction, might be spent in 

 the employment of our own operatives of every description. Here 

 too we see that this is no matter, dependent for its importance on the 

 whims of connoisseurs, or the fancies of dilettanti, but one which 

 affects all classes of art. In truth the Nasmyths, the Bramahs, he 

 Rennies, have a much deeper interest in it than Sir Martin Archer 

 Shee or Sir Richard Westmacott: the latter indeed have rather a 

 jealousy as to the field of art being still more overcrowded, but it is 

 evident that if we increase our production of textile or other fabrics 

 in the same ratio must a demand be created for steam engines, lor 



