May 30, 1872] 



NATURE 



85 



with acre upon acre of its own wasted drbris. On the 

 crests of the heights the rociv was found to be split by 

 frosts along its joints ; numberless blocks had fallen off, 

 and the slopes below were thickly strewn with them. On 

 smoother declivities, such as those that descend from the 

 lonely and barren Beinn Bharrain, each casual torrent was 

 seen to have ploughed out of the loosened and corroded 

 granite a deep trench, which in time might get widened 

 and deepened into a lateral valley. The waste of moun- 

 tains could not be more eloquently revealed. As the 

 party in long fde threaded its way through these soli- 

 tudes, a feeling uhich had been growing all day found at 

 last expression, and as the scattered scouts who, in the 

 exuberance of yoimg life, had dispersed up and down hill 

 on either side of the main body, gathered together into 

 one merry company at the edge ot the dark and lonely 

 Corrie au Lachan, it was unanimously agreed that had 

 this band of stone-breakers seen nothing more than these 

 proofs of how a mountain may be sculptured, the lesson 

 was worth all the trouble and fatigue of the excursion. 



NOE'S THERMO-ELECTRIC BATTERY 



A SUPPLY of dynamic electricity is almost as requisite 

 -'*- now for the lecture table as the supply of gas or water. 

 The decomposition of water and various other liquids, 

 the decomposition of certain gases in Hoffmann's U tube, 

 with the aid of Rhumkorff's coil, and the physical test 

 afforded by the passage of electricity through vacua con- 

 taining traces of different gases, are most constant lecture 

 experiments. And no wonder : the brilliant purple light 

 afforded by the passage of electricity through a nitrogen 

 vacuum, is, perhaps, the best and most reliable, if, indeed, 

 it be not the only, test for nitrogen gas ; while the decom- 

 position of water gas, of ammonia, and of marsh gas, are 

 experiments of the utmost importance in modern 

 Chemistry. Hitherto the chief drawback has been the 

 voltaic battery ; the setting up of the battery before the 

 lecture, the taking it to pieces afterwards, the constant 

 amalgamation of the zinc plates, the consumption of zinc 

 and acid, the fumes — in a word, the general inconvenience 

 inseparable from any form of voltaic battery, but reduced 

 to a minimum in Sir William Thomson's constant gravi- 

 tation battery. The former of these inconveniences are 

 more apparent, when, as is often the case, the battery is 

 only required for five minutes during the whole lecture. 



Hence, when a statement recently appeared in Poggen- 

 dorff s " Annalen," to the effect that a thermo-electric battery 

 of great power had recently been constructed in Vienna by 

 Franz Noe, we were glad to take the first opportunity of 

 trying to what extent it could replace the ordinary voltaic 

 battery for the lecture table. It was stated that the 

 battery could readily decompose water, work a Rhum- 

 korff's coil, and powerfully excite electro-magnets. As we 

 understand from the maker that the battery about to be 

 described is the only one in use in this country, it may be 

 of interest to give a short account of its capabilities. 



The battery consists of eighty elements, which are 

 heated by eighty small Bunsen burners, the cooling of 

 the opposite extremities being effected by broad, blackened 

 sheets of copper, which of course radiate freely. The 

 negative metal is a silver-white alloy drawn into wire, and 

 partially enclosed in small copper cyhnders to protect it 

 from the direct action of the tlame. The positive metal 

 is a dull grey alloy extremely crystalline and brittle, and 

 is cast into cylinders about 20 mm. long by 7 mm. dia- 

 meter. The composition of both these alloys is kept 

 secret. Alternate pairs are separated by small square 

 plates of mica. The elements can with readiness be com- 

 bined either for quantity or intensity. Thus the eighty 

 elements may be used together in one series, or in two 

 series of forty elements, or in four series of tv.enty 

 elements. 



The battery under consideration differs somewhat from 

 that described in Poggendorff; it is larger; a sliding 

 double groove keeps the burners in one position, exactly 

 midway between the double rows of elements ; and 

 arrangements have been introduced in order to prevent 

 radiation from the sides of the flames to the blackened 

 copper radiators, that is, to the cool end of the elements. 

 According to the maker, the battery is equal to " 8 grosse 

 Daniell'sche Elemente." The electromotive force of one 

 element, according to M. Von Waltenhofen, was found to 

 be equal to V2\ to 1-36 Jacobi-Siemens's unit, while a 

 Daniell's cell (no dimensions given; is equal to twelve of 

 these units. One Noe's elements is said to be equal to 

 1 1 of the ordinary bismuth-antimony elements. 



On testing the battery of eighty elements, we found it 

 to be somewhat weaker than we expected. It is, however, 

 very difficult to know to what extent the elements may 

 be safely heated. No definite directions are given on the 

 subject by the maker, and as the composition of the alloys 

 is kept secret, one is unable to ascertain their fusing point 

 without sacrificing a pair of elements. 



With large iron electrodes placed in a solution of very 

 dilute potash, water was decomposed by the battery at the 

 rate of 22 cub. centimetres per minute. With small pla- 

 tinum electrodes exposing less than one square centimetre 

 of surface in water rendered acid by dilute sulphuric acid, 

 10 cc. of the mixed gases were evolved per minute. One 

 of Caitfe's induction coils, capable of giving a spark 

 15 mm. long, was connected with the battery. A copious 

 stream of sparks 1 1 mm. long was produced. With a 

 small 6-inch electro-magnet, surrounded by only two coils 

 of wire, the battery produced a portative force of more 

 than 20 lbs., when the gas was turned down so as to be 

 nearly level with the orifice of the burners, and the flame 

 was distant some 9 mm. from the surface of the elements. 

 It is very possible that the battery might be heated to a 

 higher temperature than that employed for decomposing 

 water without detriment. In no case did the upper cylin- 

 ders glow with even a faint red heat. 



Here then we have an instrument which at a moment's 

 notice can be set in action, which consumes a small 

 amount of gas, is tolerably portable, and which is sufir- 

 cient for all ordinary electro-magnetic experiments, for 

 lecture demonstration of the decomposition of water, 

 ammonia, &c., and for many purposes for which a voltaic 

 battery has now to be used. Four or six of these batteries 

 would be sufficient for all purposes xave the electric light ; 

 they might be made more compact, and coidd with ease 

 be placed beneath and at one end of the lecture table. 

 The lighting of a row of gas jets would thus furnish us at 

 any moment with an abundant current of electricity. The 

 battery is, indeed, less strong than one could wish, but 

 the production of it is a step in the right direction ; and 

 we look forward to the time when powerful and compact 

 thermo-electric batteries will be found in every lecture- 

 room, and when the lighting of a row of gas jets will, 

 through the medium of such batteries, furnish us at any 

 moment with a powerful electric light. 



We are at the outset of invention in this direction ; 

 several improvements in Noes battery seem to us to be 

 both advisable and practicable. Let the elements be en- 

 larged, the brittle cylinders of alloy protected, the radia- 

 tion of heat from the sides of the row of gas jets to the 

 cool ends of the elements entirely prevented, which is by 

 no means the case now ; and, if possible, let a current of 

 cold water flow through pipes interspersed among the 

 cooling plates. Again, let the pressure and amount of 

 gas be indicated, and let the stop-cock admitting the gas 

 be furnished with a projecting pin, moving on a graduated 

 dial, so that any desired amount of gas (pre-determined) 

 can at any time be caused to issue from the burners, and 

 thus any desired strength of current (pre-determined in 

 reference to the heating eflect by ordinary electrometrica! 

 means) be obtained, G. F, Rodwell 



