January i8, 1889.] 



SCIENCE. 



35 



summer's night. But the line sketched out by Professor Brackett 

 •offers, we think, only a very slender hope of accomplishment. 



New Secondary Batteries. — Hardly a week passes but we 

 read of some new secondary battery that is to be introduced. This 

 state of affairs has a promising side and an unpromising one. It 

 shows the great need of some reliable storage-battery, and it brings 

 •out the fact that a great number of people are working at the prob- 

 lem of finding one. Some of these new cells compare very favor- 

 ably with the older and better-known types ; some of them are, in 

 all probability, not so good. One of the newest is the Johnson bat- 

 tery, which is to be manufactured in Boston. Special advantages 

 are claimed for it, but no figures are given, nor is it anywhere fully 

 •described. Two other batteries have been recently put on the 

 market, — the Macreon and the Detroit. We hope to publish some 

 ■figures as to the latter at an early date : it is a promising type of 

 cell. It is to be hoped that a year which opens with such activity 

 in storage-battery circles will develop some cell that will make 

 electric traction in our crowded cities practicable. 



Is A Vacuum an Electric Conductor? — Some time ago 

 M. Foeppl made some interesting experiments on the conductivity 

 of a vacuum ; his results tending to show that a vacuum is an in- 

 sulator, or, at best, its conducting-power is very small. The ex- 

 periment has been described in this journal. Briefly it consisted 

 in making a galvanometer whose coils were made of glass tubing 

 ■from which the air had been exhausted, and connecting it with the 

 secondary of an induction-coil, also constructed of glass tubing. 

 There was no inductive effect observed when a current was sent 

 through the primary of the coil, even when the electro-motive force 

 induced had a value of 5,000 volts. M. Foeppl concluded then 

 that an absolute vacuum would be a non-conductor, and that or- 

 dinary vacuum-tube phenomena are caused by convection. Some 

 ■of his more recent experiments tend to throw some doubt on 

 these conclusions. He placed an exhausted tube within a solenoid 

 through which he sent a Leyden jar discharge. Luminous phe- 

 nomena took place, as in an ordinary vacuum tube provided with 

 ■electrodes, at which an electro-motive force is applied. We know 

 so little, however, of the nature of luminous discharges in vacua, 

 that we can hardly consider the evidence of the last experiment so 

 ■strong as that of the first ; and while it may be possible to account 

 for either result on the hypothesis of the non-conduction, or on 

 that of the conduction of a vacuum, the former seems much the 

 more probable. 



Electric Light in the Patent Office. — From the report 

 of the secretary of the interior, we learn that arrangements were 

 made the past year with the assistance of Lieut. -Commander Bradford 

 of the United States Navy (among the most expert of electricians), 

 with the Brush Electric Light Company of Cleveland, O., for the 

 ■construction of the necessary machinery, and the arrangement of 

 wires, appliances, and lamps, for the Patent Office building, in or- 

 der to light it completely. The department will be able to furnish 

 its own light at so great a diminished cost, that it is believed the 

 saving from the average annual outlay heretofore sustained will in 

 three years reimburse the expenditure for the plant. There are 

 such vast piles of public papers, records, and documents in the 

 various rooms, halls, and cellars of the department, many of these 

 so dark as to require light throughout the day, that a mode of illu- 

 tnination which is consistent with their safety becomes of prime 

 importance. It is believed that this object has been most satisfac- 

 torily secured by the arrangements made under the direction of 

 Lieut.-Commander Bradford. Secretary Vilas avails himself of 

 the opportunity to express his sense of obligation for the great ad- 

 vantage enjoyed in the generous contribution of Lieut.-Commander 

 Bradford's expert and valuable knowledge, from which he believes 

 the electrical equipment of the department will hardly be equalled 

 in the country for safety and efficiency, procured upon the most 

 economical terms. 



Professor N. S. Shaler of Harvard University is in Washing- 

 ton, on his way to the Dismal Swamp. He will there spend a fort- 

 night in geographical and geological researches, in order to com- 

 plete an article for the next annual report of the Geological Survey. 



THE OBSERVATORY HILL RAILWAY OF ALLEGHENY 

 CITY, PENN. 



This railway has been in continuous operation since January, 

 1888, as an electric road. The line is about four miles in length. 

 For one-fourth of this distance the electric conductors are contained 

 in a sub-surface conduit. For the remainder of the line the con- 

 ductors are elevated above the roadway, being bracketed off from 

 poles erected along one side of the street. The conduit branches from 

 double to single track, and at the present terminus of the line there 

 is a conduit cross-over switch from down to up track. At different 

 points along the conduit section the conduit cuts through five other 

 street-railway tracks belonging to other companies. 



On the elevated conductor section the line is single track with 

 seven turn-outs. Double conductors are used throughout both 

 conduit and elevated conductor sections, neither the rails nor any 

 part of the conduit itself being used as a part of the electric circuit. 



Nowhere throughout the whole line is there a space fifty feet 

 long where a car will stand without the brakes being applied. 

 There are thirty-four curves on the line, not including turn-outs or 

 switches. The maximum grade is I2|^ feet in 100 feet. There is a 

 total rise of 295 feet in 4,900 feet, with an average of about six per 

 cent. The maximum grade of 12^ is on a reversed curve (radii 100 

 and 200 feet). The sharpest curve has a 35-foot radius on five-per- 

 cent grade. 



The Bentley-Knight conduit system consists of a power station, 

 — engines, boilers, and dynamo-electric machines ; a conduit run- 

 ning the whole length of the line, containing the conductors which 

 convey the electric current to the motors ; and hanging connections 

 (ploughs) which pass through the conduit slot, and, sliding along 

 the conductors, maintain unbroken connection between the motors 

 and the source of power. The electric conductors are accessible 

 only to regular employees, furnished with special tools, while the 

 current used, even in roads of the heaviest carrying capacity, can- 

 not injure either life or property. 



The conduit, which contains the conductors and supplies the cur- 

 rent to the motors along the line, can be placed at any point where 

 the opening of the slot will be below any part of the car-body. In 

 constructing a conduit line, the iron yokes shown in the accompany- 

 ing figure are set up from four to six feet, apart, and the conductors 

 set against the insulators which support them at each yoke. The 

 electrical connection between the different lengths of conductor are 

 then made, the slot-steels set on the yokes, and the slot-steels and 

 yokes firmly bolted together, leaving a slot opening at the surface of 

 the street of only five-eighths of an inch. Attention is especially 

 directed to that form of Bentley-Knight conduit which permits the 

 width of the slot to be regulated, the slot rails to be removed, and 

 the conductors, insulators, and interior of the conduit to be in- 

 spected, without disturbing the pavement. The conductors are 

 copper bars connected by expansion joints, and are of sufficient 

 size to carry the current with a loss never greater than five per cent. 

 The fact that the conduit can swerve from a straight line to avoid 

 obstructions, and can be laid outside of the track wherever desired, 

 greatly decreases the expense and difficulty of laying. 



Electrical connection between the motor and the conductors in 

 the conduit is effected by a contact-plough, which consists of a flat 

 frame, hung from the car by transverse guides (on which it is free 

 to slide the whole width of the car), and extending thence down 

 through the slot of the conduit. It is so constructed as to adjust 

 itself to all inequalities of road or conduit. This frame carries two 

 flat insulated conductor-cores, to the lower ends of which are at- 

 tached, by spring hinges, small contact-shoes, which slide along in 

 contact with the two conductors in the conduit. At the upper ends 

 are attached connections leading to the motor. This plough can 

 be inserted or withdrawn through the slot at will, the spring hinges 

 allowing the contact-shoes to straighten out into line with the con- 

 ductor-cores when the plough is pulled upward. By no accident, 

 therefore, can any thing be left behind in the conduit to obstruct 

 succeeding cars. The plough-guides are hung on transverse axes, 

 and are held in a vertical position by a spring-catch that gives way 

 when the plough meets an irremovable obstruction, and allowing 

 the plough to be thrown completely out of the conduit without in- 

 jury, it being also immediately replaceable. The frame of the 



