SCIENCE. 



[Vol. XIII. No. 309 



gregate capacity of about 8,000 lamps. Dynamos and engines are 

 on the same floor, every part of which is constantly under the eye 

 of a single attendant. Both engines and dynamos stand on brick 

 foundations, the floor itself being of cement. Each engine is belted 

 direct to its dynamo, no power being wasted in transmission ; and 

 the subdivision of power enables the wide fluctuations of load to 

 be met by stopping and starting any engine and dynamo as needed, 

 thus operating the whole station under the highest possible eco- 

 nomical conditions at any moment. The steam-pipe is brought 

 along the engine-room overhead, and the engines e.xhaust into a 

 main laid in a covered trench underneath the floor, every part being 

 accessible. All drips and overflows are run into a sewer. Two 

 exciting dynamos are provided, as shown on the left of the dynamo- 

 room, each adequate to supply current to the fields of all the alter- 

 nating dynamos of the station, and each driven independently by 

 its own engine. But one engine and exciter is therefore run at any 

 time, the other standing ready as a relay in emergency. Moreover, 

 the position of the engines and exciters is such that by changing a 

 belt either engine can drive either exciter, and thus the chance of 

 possible stoppage is reduced fourfold. The Westinghouse Com- 

 pany regard this latter arrangement as representing the best possi- 

 ble engineering, and strongly urge it upon every station of any con- 

 siderable magnitude. Two overhead travelling-cranes traverse the 

 whole length of the building over the engines and dynamos. 



In a station so arranged, the labor is reduced to a minimum. 

 With natural gas, of course, but one fireman is required ; firing 

 with coal, two firemen will be on duty in the first run of the even- 

 ing, and one in the second run. But one attendant is required in 

 the dynamo-room at any time, the lightness of his duties permit- 

 ting him to give all necessary attention to the engines, dynamos, 

 exciters, and switch-board. It is obvious that this general plan can 

 be advantageously followed in most instances. 



COAL-MINING MACHINES OPERATED BY ELEC- 

 TRICITY. 

 There has probably been no greater advance in the mining-field 

 effected during the past decade than the general introduction of 

 electricity for power and lighting purposes. 



The advantage of using electricity, its simplicity, compactness, 

 safety, cleanliness, and reliability over the use of steam for power, 

 were early recognized by mining engineers, and electricity is now 

 generally regarded as the most convenient agent at the miner's dis- 

 posal for transmitting his power into the interior of the mine. 



One of the newest and latest applications of electric power to 

 mining-work can be seen daily in operation at Mr. T. C. Heimes's 

 " Drane Colliery," near Osceola, Clearfield County, Penn. Here a 

 most interesting application of motors for mining-work has been 

 devised by Mr. F. M. Lechner for operating a coal-cutter by elec- 

 tricity. 



Mr. Lechner is well known as being not only the first inventor of 

 coal-cutting machinery, but also the first to operate compressed air 

 in mines for this purpose. His long practice and experience in the 

 coal-mining field have made him familiar with all the difficulties at- 

 tending the use of machmery in mining-work, and, ever since elec- 

 tric power has been in use for industrial purposes, he has made a 

 study of the problems in adapting electric power to this work. 



It soon became evident to Mr. Lechner that the best results could 

 only be obtained by operating the motor and cutter apart, as other- 

 wise the size and weight of the cutter with the motor mounted 

 upon it would prevent its easy transportation in the mine. 



In order to do this, the following arrangement has been adopted 

 in the mine before mentioned, and has proved very successful. 

 The motor, which is a 10 horse-power of the Sprague type, is 

 mounted upon a truck running upon rails, so that it can be very 

 easily handled and hauled from one position to another, as occasion 

 requires. The entire weight of the motor is less than 1,000 

 pounds. 



The cutter operated by the motor, which in this case is the " New 

 Lechner," is set in position in the room to be cleared, and is con- 

 nected with the motor by a five-eighths inch rope belt, running in 

 V-shaped grooved sheaves, one being on the motor, and the other on 

 the cutter. 



This connection is long enough to allow the motor to be operated 

 30 feet away from the cutter, and the motor has been set in a 

 position in this mine 1,600 feet away from the dynamo. The 

 motor is held in position by guys at the point of use. 



By means of screw-jacks that can be easily adjusted to any 

 height, with loose sheaves upon them, the cutter can be operated at 

 any angle from the motor ; and the connection is made taut by 

 moving the truck upon which the motor rests, and securing it in the 

 right position by guys. 



AH mining engineers are familiar with the difficulty attending the 

 working of the cutters in the limited space generally allotted them 

 in mines, and know how essential it is to have every machine divested 

 of every pound of surplus weight. They also know what care must 

 be exercised in moving it with great iron crowbars, to prevent in- 

 jury to the more delicate parts of the engines ; and, however care- 

 ful, how frequent it is that connecting rods and other parts are so 

 impaired that the machine has to be sent to the shop ; then how the 

 rugged action of the engines shakes every thing loose on the ma- 

 chine, however firmly they may appear to be adjusted. All this is 

 removed by the absence of the engines, the machine running as 

 smoothly as a buzz-saw, and, as a consequence, cutting with the same 

 facility. By this plan, three machines can be operated by one mo- 

 tor ; for, when one room is cut, the motor can at once be hauled to 

 another room, where a machine is in readiness and position, cut 

 that room, and pass to a third while the coal is being removed from 

 the first two, and the cutters being again placed in position. 



It was found, upon a preliminary trial of this apparatus at the 

 Osceola Mines, that by its use two men are able to excavate loo- 

 tons in 10 hours, and that they can move the cutter as often as de- 

 sired without any auxiliary aid. 



The efficiency of both dynamo and motor is over 90 per cent ; so 

 that, allowing 10 per cent drop on the line, nearly 73 per cent of 

 the power delivered to the dynamo-pulley can be depended upon at 

 the motor for work. 



It has been estimated that the cost of equipping a mine for the 

 purpose of operating machinery with electricity is only about one- 

 half the cost of equipping it with compressed air, and the price of 

 maintenance shows about the same proportion of saving. 



HEALTH MATTERS. 



The Germ Theory in Consumption. 



" What Changes has the Acceptance of the Germ Theory made 

 in Measures for the Prevention and Treatment of Consumption ? ' 

 is the title of an essay by Dr. Charles V. Chapin of Providence, to 

 whom was awarded a premium of two hundred doUars by the 

 trustees of the Fisk Fund. In this essay Dr. Chapin has given an 

 admirable rhumi of all that has been written about consumption 

 from the time of Hippocrates to the present day. After a careful 

 examination of the literature of the subject, he thinks that we are 

 justified in the conclusion that the acceptance of the germ theory 

 has made no direct or important addition either to the hygiene or 

 medicinal treatment of consumption. He thinks, however, that it 

 should have great influence. It tells us plainly what we ought to 

 do. We simply do not obey its behests. The germ theory — now 

 no longer a theory in the case of tubercular consumption — tells us 

 that we have to do with a contagious disease. Now, there is no 

 theoretical reason why a purely contagious disease like tuberculosis 

 cannot be exterminated. If we can prevent the spread of contagion 

 at all, we can prevent it entirely. The enormous value of preven- 

 tive measures, isolation, disinfection, and quarantine, is well illus- 

 trated in the history of cholera, typhus-fever, and yellow-fever in the 

 United States. By keeping out the virus of these diseases, or de- 

 stroying it when it had gained access to our shores, we have for a 

 number of years been remarkably free from these diseases, and it 

 is certain that if these precautions had not been taken we should 

 have suffered severely. For obvious reasons the suppression of tu- 

 berculosis is not so easy a matter as the suppression of cholera or 

 yellow-fever. Neither is the suppression of scarlet-fever or small- 

 pox as easy. Yet wherever the public have been educated to a 

 correct appreciation of the contagious nature of scarlet-fever, the 

 number of cases has diminished very much. Even in small-pox, 

 with its virulent contagion, it is possible, by means of isolation and 



