May 



1888.] 



SCIENCE 



227 



nected to the batteries, which really are more used for transform- 

 ing the comparatively high potential employed than for storing the 

 electrical energy. The batteries are of such a capacity that they 

 can supply one-third of the energy required during the lime that 

 the maximum number of lights exceeds the capacity of the central 

 station. If the maximum energy required is 600 kilo-watts, the 

 central station will only have a capacity of 400 kilo-watts ; the 

 battery supplying the remaining 200 when it is needed, and being 

 charged when the demand falls below 400 kilo-watts, the capacity 

 of the station. It will be found, however, that this plan does not 

 utilize the storage-battery to the full extent possible, as the central 

 station will be idle for part of the twenty-four hours. What it 

 does, however, is to diminish the size of the central station and 

 equipment by one-third, and allow the electrical energy to be dis- 

 tributed at a high potential, by comparatively small conductors. 

 The potential Mr. Crompton proposes to use is in the neighborhood 

 of 450 volts, a value which seems rather low. 



For the alternating system a potential of 2,000 volts is assumed, 

 with a transformer for every one or two houses. Calculating the 

 cost of installing the above plants, Mr. Crompton finds that the 

 alternating system will come to £^7,^40 ; the direct system, with 

 storage-batteries, ^59.762. In calculating the running expenses it 

 is assumed that the batteries deteriorate only fifteen per cent per 

 year, an extremely low estimate. The following is the estimate of 

 working expenses for a year : — 



1 Accumulator. 



Transformer. 



Materials (coal, etc.) 



£2,517 OS. od. 

 1,995 

 4,086 10 



£4,648 OS. od. 



Labor and salaries 



2,608 3 





4,683 5 





Total 



11,939 13 

 ■ 3-75d 



8,598 10 

 2.7d 







These results, provided they were true, would be very encourag- 

 ing, since they would allow electric lights to be sold at a price that 

 would correspond to gas at seventy-five cents per thousand, with 

 an extremely handsome percentage on the original outlay. Mr. 

 Crompton has omitted in his estimate the cost for rent and attend- 

 ance at the batterv stations, — items that would add about ^i.ooo 

 per year to the accumulator account, but which would still give a 

 balance in its favor. While in this country the conditions of dis- 

 tribution are different, a plant of 10,000 lights being smaller than 

 would be built in any large city, yet the comparative values given 

 will not be greatly modified ; and when we consider that here the 

 distribution of power must be taken into account, and credited to 

 the direct system, — power distribution being impossible at present 

 with alternating currents, — the moral of Mr. Crompton's figures 

 seems to be that the alternating system has no place in densely popu- 

 lated centres, but must be relegated to towns and the suburbs of 

 cities, where there is a field for it as wide as its most enthusiastic 

 disciples can wish. 



Electric Street-Cars in Baltimore. — In the last few 

 weeks a car equipped with electric motors and storage-batteries 

 has been running in Baltimore, with a success that promises at 

 least a systematic experiment to determine the expense and the 

 value of the system. The condition of the street-railway tracks in 

 Baltimore — the heavy grades and sharp curves — is such that the 

 demand on a secondary battery is very trying ; there is also a heavy 

 demand on the motors, which must develop as much as 20-horse 

 power for considerable distances. In order to avoid too heavy a 

 discharge-rate from the battery, a larger number of cells are em- 

 ployed than would be ordinarily used. The details of the equip- 

 ment are as follows : the car is a large sixteen-foot car, furnished 

 with two Sprague motors of 7-J-horse power each, capable of work- 

 ing up to over lo-horse power. The gearing is the ordinary gear- 

 ing of the Sprague system, and has been described in this journal. 

 The weight of the motors and gears is about 1,600 pounds. The 

 battery consists of 126 cells placed beneath the seats, arranged in 

 boxes of nine cells each. The cells are of the grid type, manufac- 

 tured by the Accumulator Company under the patents of Faure, 



Sellon, Swan, etc. ; the Electrical Storage Company of Baltimore 

 having the patent rights for Maryland, the District of Columbia, 

 and West Virginia. The cells weigh about 4,200 pounds, and the 

 total weight of the car is 13,000 pounds. Before the car was tried, 

 there was considerable doubt, even among members of the com- 

 pany, whether it would successfully take the heavy grades that the 

 track offers. It has been running, however, for several weeks with 

 excellent results : it ascends the steepest grades with ease, and 

 much faster than do horse-cars ; there is very little noise ; the car 

 is under most perfect control ; and, as far as performance goes, it 

 is a decided success. The question of cost has yet to be settled. 

 If we take a number of cars, and if the street-car company sup- 

 plies its own power, the cost per car per day for power will not 

 exceed ^1.75, counting all the expenses excepting only the de- 

 terioration and handling of the battery. As the cost of horse- 

 power per car per day for the same service is not less than $6, the 

 margin for repairs and attendance is about $4.25 per car per day. 

 Whether that amount will suffice can only be determined by trial ; 

 but if every precaution is taken, and if the battery and motor are 

 properly designed for the work they have to do, it is probable that 

 the expenses will not be greater than the cost of horses. As to 

 the increased comfort, there is no question. 



Suspensions tor Galvanometers. — Dr. G. A. Liebig, in 

 an article in the Electrical World, gives the results of some ex- 

 periments on different kinds of silk for galvanometer suspensions. 

 If ordinary silk fibres be used to suspend delicate astatic systems, 

 there will be found some trouble from capricious movements of the 

 needles. Dr. Liebig shows that these are probably due to two 

 things. In the first place, an ordinary fibre of silk obtained from 

 a cocoon consists of two single fibres surrounded by a " gummy 

 substance of a gelatinous nature," the last making up about one- 

 third the bulk of the fibre. The disturbing effects seem due to, in 

 the first place, not separating the two parts of the double fibre ; 

 and, in the second place, to the changes in the outer gelatinous 

 coating from moisture, etc. The remedy lies in using only a single 

 fibre, and in washing it in hot water, dissolving off the coating. 

 The variety of silk known as ' tussus ' is especially recommended, 

 a single fibre being able to sustain from five to seven grams, as 

 against two grams for ordinary silk. 



BOOK-REVIEWS. 



Ancient Legends, Mystic Charms and Sicperstitions of Ireland. 



By Lady Wilde. Boston, Ticknor. 12°. §2.50. 



The present volume contains a great number of legends and 

 current beliefs of Ireland, collected by an enthusiastic lover of the 

 island and of its people. Many of the legends were directly ob- 

 tained from oral communications, and the simplicity of the style in 

 which they are told adds to their attractiveness. The contents of 

 the volume are of great variety. A number of legends treating 

 mainly of fairies and kindred subjects is followed by a description 

 of festivals and myths referring to their meaning and origin. Mar- 

 riage rites and mortuary customs are fully described, and in read- 

 ing these we were much pleased with the author's remark that 

 there is nothing derogatory to grief in the idea of hired mourners. 

 " On the contrary," she says, " it is a splendid tribute to the dead 

 to order their praises to be recited publicly before the assembled 

 friends ; while there is something indescribably impressive in the 

 aspect of the mourning women crouched around the bier." It is 

 this endeavor of the author to present usages, superstitions, and 

 beliefs from the standpoint of those who hold to them, which makes 

 the book particularly valuable, and attractive to the reader. It 

 seems to us that the author has been eminently successful in this 

 attempt. A special chapter treats of medical superstitions. A 

 comparison of these remarks with Mr. Mooney's paper mentioned 

 in a recent number of Science will be of interest. Legends refer- 

 ring to the sidhe and banshee receive special attention, while there 

 are comparatively few treating of the saints and their exploits. The 

 theories of the author regarding the origin of the various legends 

 and customs occupy only a small portion of the book, and will 

 hardly stand a severe test. The appendix, which treats principally 

 of the antiquities of Ireland, of early Irish art and the ancient 



