November 22, 1889.] 



SCIENCE 



349 



accumulators of suitable capacity and tension. For the net of 

 •conductors, in consequence of the extended line of streets to be 

 traversed, the five-lead system has been selected. The leads are 

 not cables, as has hitherto been customary, but uncovered rods of 

 copper, resting on insulators of porcelain, and laid in channels of 

 cement. These channels will be mostly carried underneath the 

 flags of the footway. The distribution of the current takes place 

 so that each of the four successive current circuits formed by the 

 five-lead system shows a working tension of no volts. The e.xecu- 

 tion of the entire electrical installation, original and in many respects 

 interesting, is intrusted to the firm Naglo Brothers of Berlin, 

 who will use for storing up electric energy " Tudor " accumu- 

 lators made by the firm Miiller & Einbeck of Hagen. The above- 

 mentioned Siemens " five-lead system " has not yet been practi- 

 cally applied in any electrical installation ; but the firm Siemens & 

 Halske is executing two extensive installations on this system, — 

 ■one at Vienna, and the other at Trient. These two installations 

 will be shortly in operation, and as many doubts have been raised 

 concerning the practicability of this system, which is a further de- 

 velopment of the three-lead system, and is hence regarded as too 

 complicated, the inauguration of the Siemens installations is awaited 

 in technical circles with no little interest. 



Lens Images made Visible by Electric Current. — In 

 the Phoiographisches Archiv, Herr R. E. Liesegang, son of Dr. 

 Liesegang of Dusseldorf, describes an apparatus with which it is 

 possible to render lens images visible at an indefinite distance from 

 the original object by means of the electric current. The instru- 

 ment is based on the well-known principle that an electric current 

 is produced by light-waves. If light strikes upon one or two 

 platinum, silver, or copper plates, which are arranged in the form 

 of a galvanic element, this gives rise to an electric current. If the 

 exposed plate consists of a large number of insulated metal wires 

 of small diameter, lying very closely together, and if some of these 

 wires are exposed, others not, then, of course, the electric current is 

 produced only in these exposed wires. If the wires are conducted 

 to another analogously constructed plate, which may be placed at 

 any distance from the first one, then the electric current will also 

 here be produced only at the parts correspondent with the exposed 

 wires of the first plate. By coating the second plate with any sub- 

 stance which by galvanic decomposition undergoes a visible change, 

 ■exposed parts of the second plate can be easily distinguished from 

 the unexposed ones. If, therefore, an image is projected by means 

 of a lens upon the first plate, the same image will be obtained on 

 the second plate. 



An Electric Radiation Meter. — At the meeting of the 

 London Physical Society, Nov. i, Mr. W. G. Gregory read a paper 

 on " A New Electric Radiation Meter." He stated that the meter 

 consists of a long fine platinum wire attached to a delicate magni- 

 fying spring of the Ayrton and Perry type, and stretched within a 

 compound tube of brass and glass. At the junction between the 

 wire and spring a small mirror is fixed. When the tube is placed 

 parallel to a Hertz's oscillator in action, the mirror is turned in a 

 •direction indicating an extension of the wire. The arrangement is 

 so sensitive that an elongation of ^^^-^^ of a millimetre can be de- 

 tected ; and, when placed at the distance of a metre from the os- 

 cillator, the apparent extension is such as would correspond to a 

 •change of temperature of 0.003° C. By its aid the author has 

 roughly verified Hertz's statements, that at considerable distances 

 the intensity of radiation varies as the inverse distance ; but, before 

 he can proceed further, it is necessary to greatly increase the sen- 

 sibility of the apparatus, and, with a view of obtaining some sug- 

 gestions in this direction, he exhibited it before the society. Pro- 

 fessor Perry asked if the electro-motive force required to produce 

 the observed results had been calculated ; he also believed that the 

 sensibility might be increased by using copper instead of platinum, 

 and replacing the spring by a twisted strip. Mr. Blakesley inquired 

 whether the effect of increasing the capacity of the ends of the wire 

 had been tried. Mr. Boys said, that, if the observed effect was due 

 to rise of temperature, he would like to see it measured thermally. 

 He also thought the effect might be due to extension caused by 

 rapid electric oscillations in some such way as the elongation of an 

 iron bar caused by magnetization. In answer to this. Professor S. 



P. Thompson said the matter had been investigated experimentally, 

 but with negative results. Professor Herschel suggested the use 

 of a compound spring such as is used in Breguet's metallic ther- 

 mometers. In reply Mr. Gregory said that he had estimated the 

 electro-motive force by observing that a Leclanche cell through 50 

 ohms produced about the same result. No improvement in sensi- 

 tiveness was obtained by using copper wire or by increasing its 

 capacity, and attempts to measure the rise of temperature by an 

 air thermometer had been given up as hopeless. 



Driving Tuning-Forks Electrically. — Mr. W. G. 

 Gregory, at the meeting above mentioned, also read a paper on " A 

 Method of Driving Tuning-Forks Electrically." In order to give the 

 impulses about the middle of the stroke, the fork is arranged to 

 make and break the primary circuit of a small transformer, the 

 secondary circuit of which is completed through the electro-magnet 

 actuating the fork. The prongs of the fork are magnetized and 

 receive two impulses in each period. Another device was sug- 

 gested, where the prongs respectively operate contacts which 

 successively charge and discharge a condenser through the coils of 

 the actuating magnet. Professor S. P. Thompson said the methods, 

 if perfect, would be of great service, and suggested that a fork so 

 driven be tested optically by comparison with a freely vibrating 

 one. He regarded the mercury contacts used as objectionable, for 

 their capillarity and adhesion would probably cause the impulses 

 to lag behind the appointed epochs. Professor M'Leod remarked 

 that Lissajou's figures gave a satisfactory method of testing the 

 constancy of period, and could be readily observed without using 

 lenses, and in reference to liquid condensers, suggested by the 

 author for his second device, said that platinum plates in sulphuric 

 acid were found to disintegrate when used for this purpose. He 

 thought lead plates would prove suitable. Professor Jones, who 

 read a paper on a similar subject in March last, said he now used 

 bowed forks, with which to synchronize the speed of the disk 

 there described ; and the frequency is determined by causing 

 the disk to complete the circuit of his Morse receiver once each 

 revolution. 



On Electrifications due to Contact of Gases and 

 Liquids. — A paper on this subject was read by Mr. J. Enright be- 

 fore the Physical Society above alluded to. For some time past 

 the author has been studying the electrical phenomena attending 

 solution by connecting an insulated vessel in which the solution 

 takes place with an electrometer. As a general rule, no efifect is 

 observed if nothing leaves the vessel, but, when gases are produced 

 and allowed to escape, the vessel becomes charged with positive or 

 negative electricity, depending on the nature of the liquid from 

 which the gas passes into the air. As an example, when zinc is 

 placed in hydrochloric acid, the deflection of the electrometer is in 

 one direction, while the liquid is chiefly acid, but decreases and re- 

 verses as more and more zinc chloride is produced. From such 

 observations the author hopes to obtain some information relating 

 to atomic charges. Owing to the lateness of the hour, the latter 

 portion of the paper and the discussion on it were postponed until 

 the next meeting. For the above reports of the papers read at 

 the meeting of the London Physical Society, we are indebted to 

 Engineering. 



NOTES AND NEWS. 



A Mr. M. W. Dewey of Syracuse, N.Y., has patented an elec- 

 tric refrigerator, based on the well-known fact that a cui-rent of 

 electricity passed in the proper direction across the junction of two 

 dissimilar metals cools the joint. While Mr. Dewey's apparatus is 

 all right as far as the principle is concerned, we would rather not 

 express any opinion on its practical value just yet. 



— Beginning with January i next, the Rev. T.De Witt Talmage, 

 D.D., will become one of the editors of The Ladies' Home Journal 

 of Philadelphia. The famous preacher will have a regular depart- 

 ment each month, written by himself, with the title " Under My 

 Study Lamp." His first contribution will appear in the January 

 number of the journal. Dr. Tal mage's salary is said to be one of 

 the largest ever paid for editorial work. 



