March 23, 1888.] 



SCIENCE. 



141 



months' standing, in a child two years of age, he obtained a rapid 

 cicatrization by means of grafts from a fowl. He first tried grafts 

 of frogs' skin, but as these proved to be repulsive to patients, and 

 did not give very good results, he substituted others from the fowl ; 

 and the wound, which measured three inches by two and a half, 

 had completely healed in two months. He had been equally suc- 

 cessful in other and subsequent cases. He takes the skin from 

 beneath the wing of a chicken, carefully securing the subjacent cell- 

 ular tissue, but avoiding adipose tissue. The transplanted pieces 

 varied from a sixth to a third of an inch in size, and they were main- 

 tained in position by means of a little cotton-wool and iodoform 

 gauze. The skin of birds and fowls has the advantage of being 

 supple, delicate, and vascular : it adapts itself readily to the surface 

 of the wound, and adheres without undergoing absorption. 



The HUM.A.N Breath. — Professor Brown- Sequard has recently 

 been making experiments to determine whether the human breath 

 was capable of producing any poisonous effects. From the con- 

 densed watery vapor of the expired air, he obtained a poisonous 

 liquid, which, when injected under the skin of rabbits, produced al- 

 most immediate death. He ascertained that this poison was an 

 alkaloid, and not a microbe. The rabbits thus injected died with- 

 ■out convulsions, the heart and large blood-vessels being engorged 

 with blood. Brown-Sequard considers it fully proved that the ex- 

 pired air, both of man and animals, contains a volatile poisonous 

 principle which is much more deleterious than carbonic acid. 



ELECTRICAL SCIENCE. 

 Electrical Traction. 



In the last two or three years a number of street-car lines have 

 been equipped with electric motors, and most of them have been 

 successful in spite of the inexperience of those who have done the 

 work, — an inexperience due to the newness of the field. The 

 number of electric railroads under way is increasing rapidly, and 

 for certain classes of work the motor seems destined to take the 

 place of the expensive and overworked car-horse. 



As yet the greater part of the lines equipped have been for city 

 tramways, generally in the suburbs, where there is comparatively 

 little street traffic. This, however, is only a beginning, more useful 

 in the experience it gives, and in the problems that are brought up 

 and solved, than in the absolute results : for the question of the 

 application of electricity to traction is a very broad one, and does 

 not stop at street-railways. The elevated railroads may be run by 

 ■electric motors ; already motor cars are used in mmes, where there 

 is an extended field for their use; and it is possible that a few years 

 will displace the steam locomotive, and substitute in its place 

 powerful electrical locomotives. 



There is no apparatus for the transformation of energy that com- 

 pares in simplicity and efficiency with the dynamo-electric machine 

 and electric motor. The steam-engine transforms perhaps fifteen 

 per cent of the energy of coal into mechanical work ; while the 

 •efficiency of a good dynamo may be ninety-two per cent, and a 

 motor may have as high an efficiency. If, therefore, we transform 

 mechanical work into electrical energy by a dynamo, and retrans- 

 form it to mechanical work again by a motor, we have a total loss 

 of perhaps fifteen per cent. It may be easily shown that in many 

 cases it would be profitable, by taking advantage of the higher effi- 

 ciency of large-power plants, and the comparatively small cost of 

 attendance, repairs, etc., per horse-power, to generate all the 

 mechanical energy needed in a district at some central station, and 

 -distribute it by dynamos and motors to the consumers, displacing 

 the small steam or gas engine plants previously used. 



For traction-work the problem is not to replace stationary steam- 

 engines or gas-engines, but to replace horses, cables, and locomo- 

 tives. This problem is being attacked, and will doubtless be at 

 least partially solved. 



Before taking up the relative merits and cost of different systems, 

 let us consider the broad questions that are involved. The ques- 

 i;ions are, (i) How can we best produce the electrical energy 

 needed ? (2) How can we best get it to our motors .' and (3) 

 After we get it there, what is the best way to apply it to traction .' 



Under the first head there are a good many things to consider, 

 -and many of these can only be answered by knowing the exact con- 



ditions of our installation. We can say generally that for a given 

 horse-power needed at our motor we should so choose our source 

 of power and location of generating-station that the interest on first 

 cost of plant and conductors (supposing we use them), the total 

 depreciation, and the cost of the power generated, should be a 

 minimum. 



We will discuss these questions more fully when we come to the 

 question of cost. To show the nature of the problem that might 

 arise, suppose we have a railroad line from Philadelphia to New 

 York to be run by electric motors. We would possibly find it best 

 to have a number of generating-stations along the line, at distances 

 apart of, say, twenty miles. Now, if there were no natural sources 

 of power near the tracks, we would have to calculate the best dis- 

 tances apart for these stations, knowing the cost for a horse-power 

 with plants of different sizes, the cost of copper for conductors, the 

 cost of a ton of coal at different points on the line, etc. The prob- 

 lem would not be a difficult one. If, however, there was at some 

 distance from the line a source of natural power, — a waterfall, 

 for example, — we would have to redistribute our stations, and cal- 

 culate whether it would cost less or more to utilize the waterfall, 

 decreasing the cost of power, in that we do not have to pay for 

 coal, but increasing the size of plant for a given electrical energy at 

 the line (for we must supply the needed energy plus the loss on 

 our lines), and increasing the outlay in conductors. Of course, this 

 is all a very definite question, presenting little difficulty to the 

 electrical economist. When we consider that some railroad lines 

 have distributed near them water-power capable of running all of 

 their trains, with help at long intervals from steam-generating 

 stations (even windmills are not to be despised in some cases), and 

 when we further consider that the conditions are much simpler 

 than in city traffic (we can use high potentials and unsightly de- 

 vices if we choose), it encourages one to predict a future for electric 

 railroads. 



If, as I have so far assumed, we are going to transmit the electri- 

 cal energy to the motors by conductors, it is evident that the poten- 

 tial we can use comes in as a factor. In cities we are usually limited 

 to a comparatively low potential, — a maximum, say, of five hun- 

 dred volts. This has the effect of locating our generating-station 

 as near the line as possible, — in the middle of the line if we can 

 get it there, — for the cost of conductors would be great if the sta- 

 tion were too far from the line. We will have more to say on this 

 in any early number. 



Electrical Treatment of Sewage. — Mr. William Web- 

 ster, F.C.S., has patented a process of purifying sewage by means 

 of the electrical current. The pollution of rivers by the sewage of 

 large cities is a constant source of danger to health ; and, accord- 

 ing to the London Standard, _£i,ooo,ooo is to be spent in attempt- 

 ing, by the employment of chemicals, to purify the London sewage. 

 Mr. VVebster's plan consists in sending a current of electricity from 

 metallic electrodes through the sewage. The result, in experiments 

 made on a very small scale, is to set the solid particles held in sus- 

 pension in motion, " a kind of procession taking place from the top 

 downwards, and from the bottom upwards. The sum-total of the 

 movements consists in landing the suspended particles at the top of 

 the liquid." " So prompt is the effect of the electric current that 

 in twenty minutes a volume of opaque sewage becomes perfectly 

 transparent, except at the top, where the organic matter collects in 

 a semi-solid form." " From results already obtained it is calculat- 

 ed that the cost of the electrical treatment of the London sewage 

 would be about £p.'^,ooo per annum. The annual outlay for chemi- 

 cals is expected to be _^i 8,000 for lime and iron, and ;£ 12,000 for 

 permanganic acid, making a total of ^30,000, a balanceof ;/j5,ooo in 

 favor of the electrical method. It would seem 'that Mr. Webster's 

 experiments have, as yet, been on a small scale. If the practical 

 results bear out what has been done in the laboratory, the process 

 will be of the greatest importance. 



Transformers. — Two papers on this subject, read before the 

 Society of Telegraph Engineers and Electricians, — one by Mr. 

 Kapp, the other by Mr. Mackenzie, — have excited considerable 

 discussion and interest on this subject of commercial induction- 

 coils. Mr. Kapp's paper treats of the relative merits of different 

 forms of transformers, and his methods are simple and easy of 



