October 19, 1888.] 



SCIENCE 



187 



Parliament regulating electric distribution in the latter country. 

 The rapid progress in this country he ascribed partly to the fact 

 that capitalists here have sufficient technical knowledge to cause 

 them to take up and actively develop new scientific discoveries. 

 Professor Forbes called attention to the fact that storage-batteries 

 have not found favor in America, all of the lighting being tlone di- 

 rectly from the machines. The objection against depending on 

 moving machinery entirely is the possibility of a break-down put- 

 ting a district in darkness, but experience has shown this fear to be 

 groundless. The Edison station in Pearl Street, New York, has 

 only stopped once in seven years, and it has been working night 

 and day. 



The greater part of the author's paper was spent in describing 

 the Westinghouse alternating-current system. At the end of last 

 year this com|)any had 153,285 incandescent lamps installed, fed 

 from 152 stations : at present the number of lamps in use exceeds 

 300,000. The greatest trouble the Westinghouse people have had 

 to encounter has been from the short-circuiting of their overhead 

 mains from falling telegraph and telephone wires. This difficulty 

 is overcome by subdividing their dynamo power and the circuits. 

 Some of the stations are worked by natural gas, the fire under the 

 boilers being automatically regulated so that one man can attend to a 

 station of i,ooo-horse power. At first the hydrogen in the gas at- 

 tacks the iron of the boilers, but after a time the metal gets into a 

 condition in which no further delerioralion lakes place. Instead of 

 using a small number of large engines, it has been found economi- 

 cal to drive the dynamos from a number of comparatively small- 

 power, high-speed engines. This subdivision has the additional 

 advantage of guarding against a break-down. A commendable 

 feature of practice in America is the adherence to a few types of 

 ■dynamos and converters. This allows them to be made cheaply ; 

 and all of the parts are interchangeable, so any damage can be 

 repaired quickly and with little cost. The following tables give 

 particulars of the construction of converters and dynamos : — 



Dyncwios. 



N umber of lamps ... 



Current 



Armature resistance 

 Field resistance. .. 

 Pounds of wire it 

 Pounds of wire in field 



Total weight 



Volts 



Kevolutions per minute 



Converters. 



Number of lights 



B. and S. gauge, primary. . . . 

 B. and S. gauge, secondary.. 



No. turns of piimary 



No. turns of secondary . . . . 



Resistance of primary 



Resistance of secondary . ... 

 Pounds weight finished. . . . 



Thickness of iron plate used in consiructit 



Thickness of paper insulation 



Number of plates in No. 8 converter ... . 



} o 0065 i 



Great care is taken in the insulation of the dynamos an<l con- 

 verters. The insulating materials used are mica, fibre, and a su- 



perior kind of varnish made of copal varnish and linseed-oil. The 

 period of alternation used is 8,000 complete alternations per minute, 

 and the efficiency of transformers is very high, even when not fully 

 loaded. Tests have been made showing an efficiency as high as 

 ninety-five per cent at half-load. The transformers are fixed out- 

 side the houses, either against the walls or on posts. The total 

 efficiency from ihe engine to the lamp is very high, and 600 watts 

 of energy have been supplied to the consumer for every brake 

 horse-power (746 watts) at the engine. 



Electric Lamps for Mines. 



There are very few applications of electricity in which England 

 leads this country, but one of them is in portable batteries and lamps 

 for mining-work. These are being rapidly and successfully intro- 

 duced in (he collieries of England and Wales; and the following 

 are the details of the most successful of them, taken from a paper 

 of Mr. Nicholas Watts, read before the British Association at its 

 last meeting : — 



The Swan Lamp. — Secondary battery; four cells grouped 

 together in a block of gutta-percha, which 1.= enclosed in a wooden 

 case. Luminosity, i to \\ candles for ten hours' duration; weight, 

 7 pounds ; price, $6.25 ; cost of maintenance, 7 cents per week. In 

 extensive use in South Wales. 



The Schanschieff Lamp. — Single-fluid primary battery: four 

 zinc-carbon cells in a solution of basic sulphate of mercury, about 

 36 per cent of the salt being in solution. The solution is sold at §1 

 per gallon, and 89 cents is allowed for the same quantity of spent 

 liquid with its solid residue and free mercury precipitated by the 

 cells. Luminosity (with reflector), 2 to 3 candles for nine hours' 

 duration; weight, about 5 pounds; price, S7.50; cost of mainte- 

 nance, yi cents per week. Tested at Cannock Chase, Mardy, 

 Merthyr. and elsewhere. 



The Pitkin Lamp. — Secondary battery ; four cells. Luminosity 

 (with reflector), 4 to 5 candles for ten hours' duration. The lamp 

 is fitted with a switch and resistance to regulate the electro-motive 

 force. Weight, 8 pounds; price, $10.50. Used at Llwynypia, 

 Ocean Colliery, Trevicky, and elsewhere. 



The Walker Lamp. — Primary battery ; three carbon-zinc cells 

 in a strong brass cylinder attached to an outer case of brass or cop- 

 per. The fluid is a mixture of bichromate of potash, nitric acid, 

 and sulphuric acid. Luminosity (with reflector), sufficient to enable 

 newspaper-print to be read at a distance of 12 feet; duration, ten 

 hours; weight, 7 pounds ; price, $8 ; cost of maintenance, 14 cents 

 per week. 



The Portable Electric Syndicate Lamp. — Secondary battery. 

 Luminosity (without reflector), \\ candles for \\ hours' duration ; 

 weight, 44 pounds; price, §5. The lamp is fitted with an auto- 

 matic arrangement, whereby, if an outer casing of toughened glass 

 be broken, the current is cut off to prevent explosion of fire-damp. 



The Vaughton Lamp. — Secondary battery. The plates are 

 wedged tightly in the cell, making the battery so compact that it 

 may be subjected to much rough usage without injury. Weight, 5 

 pounds ; working cost, 14 cents per week ; price, $6 to S7. 



The advantages of these lamps are, that they do not consume or 

 vitiate the air, they give a steady and more powerful light than the 

 ordinary miner's lamp, and the danger of igniting fire-damp is re- 

 duced to a minimum. With the rapid improvements in secondary 

 and primary batteries, they will soon come into universal use. 



Electric Absorption in Dielectrics. — A. Wullner, in 

 VViedcrmann's Annalen (xxxiii. p. 19), has studied the effect of 

 time on the potential of a charged condenser. It is well known, 

 that, when the specific inductive capacity of a substance is ob- 

 tained by determining the capacity of a condenser of which it 

 forms the dielectric, different values are found, according to the 

 time that elapses between the charge and the measurement. Wull- 

 ner has attempted to find some law that governs this ' absorption ' 

 of electricity by the dielectric. His method of experiment con- 

 sisted in observing, by means of an electrometer, the variations of 

 potential of a condenser which has received a determinate charge; 

 the first readings being taken at intervals of twenty seconds, the 

 rest at intervals of from one to two minutes. He experimented on 

 a glass Leyden jar, and on disks of glass, ebonite, gum-lac, par- 

 affine, sulphur, and mica. The results are, that the potential cor- 



