28o 



SCIENCE. 



being over-exposed. Mr. T. Bflas inquired whether Mr. 

 Warnerke had tried adding bichromate of potash to his 

 emulsion. The addition of bromide of silver in the case 

 of a carbon print was supposed to increase its sensitiveness, 

 but whether it did so he could not say. Mr. Warnerke in 

 the course of his reply, said he had not found the yellow 

 colour spoken of by Captain Abney, in the enamels which 

 he had made. It was possible to eliminate all the silver by 

 the use of ferric silts. With regard to Mr. Davis's sug- 

 gestion, he was afraid he must t irow cold water upon it, 

 for he did not think it could be realized unless he used a 

 developer for the clouds different from that used for the 

 foreground. He had not tried bichromate of potash as 

 mentioned by Mr. Bolas. 



ESTIMATION OF FAT IN MILK. 



The plan I adopt is as follows : — 10 grms. of milk are 

 evaporated in a platinum boat (of suitable construction), to 

 near dryness (to complete dryness if you wish to determine 

 the total solids) in the water-bath ; the boat is now inserted 

 into the extraction tube (which is plugged with a little cot- 

 ton-wool and contains a stopper in the narrow part of the 

 tube), and then connected to an upright Liebig's condenser. 

 A small tarred flask is now fixed on to the end of the ex- 

 traction tube (50 to 100 c. c. capacity) containing ether. The 

 ether is evaporated by means of hot water, and when suffi- 

 ciently condensed in the tube above, so as to completely 

 cover the platinum boat, the stopper of the extraction tube 

 is turned and the ether allowed to remain for about six 

 hours or all night if convenient. All that now remains to 

 be done is to cautiously open the stopper and allow the 

 ether and oil to flow into the tarred flask ; boil the ether re- 

 peatedly until extraction is complete. Disconnect the 

 flask, evaporate the ether dry, and weigh the oil. The 

 platinum boat may also be taken from the extraction tube, 

 dried in water-bath, and weighed, which will give the solids 

 not fat, then ignited and weighed, and we have the ash. If 

 there is any doubt in the mind ot the operator that the 

 ether has not been able to penetrate the residue, after there 

 have been several extractions made, the boat may be with- 

 drawn from the extraction tube, the residue detached from 

 its sides by means *of a small platinum spatula, and the 

 whole again returned to the extraction tube, and the opera- 

 tion of extraction repeated. When the extraction has been 

 conducted as described, there is no fear of any fat being 

 left undissolved in the residue. The following duplicate 

 analyses are the results I have just obtained from a sample 

 of milk I have reason to believe is genuine or unadulter- 

 ated. The amount of milk operated upon was 10 grms. 

 Specific gravity, i027 - 3. 



Toial solids 10.2440 10.2448 



Fat 19940 2.0001 



Solids not fat 8.2500 8.2447 



Ash 0.6940 0.6960 



William Johnson, F.I.C., F.C.S., &c. 



THE ELECTRIC RAILWAY. 



One of the novelties at the Crystal Palace, London, on 

 Easter Monday, was the opening of an electrical railway, 

 constructed by the Socidte Anonyme d'Electricite of Brus- 

 sels, on the Siemens system. On the upper terrace of the 

 Palace grounds, overlooking the charming scenery of 

 Sydenham, a miniature circular line of railway, consisting 

 of three lines of metals, has been laid down, surrounding 

 one of the ornamental ponds, and a small wooden hut 

 erected beside it as a passenger station. On this railway, 

 which is about 300 metres in length, and has a gauge of 

 about 50 centimetres, or 19 inches, between the outer rails, 

 stands the electrical locomotive. Its length is about four 

 feet ; its breadth about a metre ; its height about as much, 

 and its weight some three-quarters of a ton. It is, in fact, 

 a Siemens dynamo-electric machine, neatly boxed in, and 

 mounted on a truck with four metal wheels, and provided 

 with a break and alarm bell for its control by the man in 

 charge. A stationary engine of about eight horse-power 

 nominal, in a shed about thirty yards from the railway line, 

 drives a stationary dynamo-electric machine, from which 

 the electro-motive current is primarily obtained. Two wires 



are connected with this fixed dynamo-machine. By one of 

 them the current flowing out is conveyed to the mid-rail of 

 the railway, to which it is attached by an iron plate bolted 

 on. The second or return wire is attached to the exterior 

 rail of the railway. The mid-rail is supported upon wood 

 blocks, and is thus in a certain degree insulated. Beneath 

 the electrical locomotive a brush of iron wires sweeps the 

 mid-rail, and the electrical current is thus taken up into the 

 locomotive, where it passes through the mounted Siemens 

 machine within it, the large bobbin of which is thereby 

 caused to revolve, and the current passing away by the 

 wheels of the truck to the exterior rails of the road, is con- 

 veyed back to the stationary dynamo-machine. As the 

 current thus circulates, and the bobbin of the mounted 

 machine revolves, it drives the four wheels of the truck as 

 the locomotive moves on, hauling after it a load of nearly 

 three tons with ease at the speed we have named. 



NOTES. 



Internal Discharges of Electric Condensers. — 

 B. Villari. — The author's conclusions are that the heat 

 evolved by the internal discharge may be neglected in case 

 of feeble discharges ; beyond certain limits it manifests 

 itself and increases very rapidly with the discharges them- 

 selves ; thus the first means to augment this internal heat is 

 to make use of jars charged to a very high potential. The 

 internal discharge is sensibly augmented if the exterior 

 spark is produced between two small balls of 20 to 30 mm. 

 in diameter ; it decreasss, on the contrary, by almost one- 

 half if the spark is taken from a point and one of the balls. 

 Tne inverse is the case for the heat produced by the exter- 

 nal exciting spark. For a given charge the internal dis- 

 charge increases if the inner coating of the jar is dimin- 

 ished. 



Researches on the Change of State in the Neigh- 

 borhood of the Critical Point of Temperature. — L. 

 Cailletet and P. Hautefeuille — The authors remark that 

 near the critical point there are witnessed for very slight 

 variations of temperature, phenomena which have led An- 

 drews to regard the gaseous and the liquid states as distant 

 terms of one and the same state of matter, which may pass 

 from one to the other by a continuous series of changes. 

 It is impossible to know what is the state of the matter 

 which gives rise to the moving and wavey striae which dis- 

 place each other above the mercury on operating in the 

 vicinity of the critical point. A slow decrease of pressure 

 often shows if a tube is filled with a liquid or a gas, for in 

 the latter case the release gives rise to a general mist and 

 to liquid drops ; but this procedure furnishes no clue to 

 the nature of these striae. The authors have overcome this 

 difficulty by coloring carbonic acid with the blue oil of gal- 

 banum. They have found that these undulating striae dis- 

 solve the oil, and are consequently produced by liquefied 

 carbonic acid. They conclude that matter does not pass by 

 insensible degrees from the liquid to the gaseous state. 



On the Action of the Selenium Radiophone. — M. E. 

 Mercadier observes that the sounds produced in the selen- 

 ium receivers which he has studied result chiefly from the 

 luminous radiations. The rays of the spectrum act from 

 the limit of the blue, on the indigo side, as far as the ex- 

 treme red, and even a little beyond the red. The indigo, 

 violet, and ultra-violet rays are without perceptible action 

 in the conditions under which he has experimented. The 

 maximum effect is always produced in the yellow portion 

 of the spectrum. Radiophones with glass tube-receivers 

 containing air, in contact with a smoked surface, give a dif- 

 ferent result, the action being principally thermic. — Comptes 

 Rendus. 



Law Relating to Cables. — L EUctricite says that there 

 is some idea of appointing a commission to inquire into the 

 state of international law relating to submarine cables. 

 The Minister for Foreign affairs in France, M. St. Hilaire, 

 has stated that, in case the forthcoming Congress of Elec- 

 tricians should arrive at any decision on the subject, he 

 will send a circular to the various Governments suggesting 

 the holding of an international conference. 



