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SCIEXCE- GOSSIP. 



CONDUCTED BY TAMES QUICK. 



Extension of Wires. — A useful arrangement 

 for the measurement of extension of wires has 

 recently been described by G. F. C. Searle in the 

 Cambridge Philosophical Society"? Proceedings. 

 Two similar wires side by side have fastened to 

 their ends small rectangular brass frames 11 cm. 

 long. The stretching weights are placed below these 

 frames. A sensitive level is placed between the 

 latter, resting at one end on a micrometer screw 

 which reads to T^jth mm - This reads off the 

 length by which the loaded wire is stretched. 



Rojjtgen Bays. — An advance has been made in 

 the production of these rays by Trowbridge in 

 America. He has lately installed an equipment of 

 no less than 20,000 storage cells in the Jefferson 

 Physical Laboratory. By this means he has at his 

 disposal an electromotive force of over 40,000 volts, 

 and moreover a fairly steady current through a 

 large resistance. He has succeeded in obtaining 

 Bontgen rays of exceptional brilliancy with the aid 

 of this E. m. f.. which yield negatives of great con- 

 trast. One great advantage of this new method of 

 generating the rays is the possibility of exactly 

 regulating the current and electromotive force 

 which is necessary to excite the rays. This has not 

 hitherto been possible. "When the X-ray tube is 

 first connected to the battery terminals no current 

 flows. The tube must be heated with a Bnnsen 

 burner. At a certain critical temperature the 

 tube suddenly lights up with a vivid fluorescence, 

 and the rays are then given off with great 

 intensity. 



Badio-actiye Bodies. — The radio-activity of 

 these bodies has now been tested at low tempera- 

 tures, and II. Curie has found that at the tempera- 

 ture of liquid air they continue to excite fluorescence 

 in uranyl-potassinm sulphate. Badio-active barium 

 chloride becomes more luminous at that tem- 

 perature. Badium has also been tested at the 

 above temperature by Behrendsen. using the 

 electrometer method. In this case, however, it 

 was found that cooling the preparation reduced 

 its radio-activity by more than one-half. On heat- 

 ing it up again to the normal temperature, a slight 

 increase of radio-activity was discovered. 



Gallon's Whistles.— In a modified form of 

 Galton's whistle, devised by Mr. T. Edelmann. the 

 blast of air from a ring-shaped mouthpiece im- 

 pinges upon the sharp edge of the pipe, which is 

 also circular, and can be brought to within anv 

 desired small distance from the mouthpiece. This 

 whistle gives very strong notes, whose pitches can 

 be studied by means of Kundt"s dust figures. It 

 has been found that the highest limit of hearing 

 is a little beyond 50.000 complete vibrations per 

 second. By making the diameter of the pipe as 

 small as 2 mm., Edelmann has succeeded in con- 

 structing pipes giving the very high pitch of 

 170,000 vibrations per second. 



Atmospheric Electricity. — Some work has 

 been done by M. Brillouin upon the nature of 

 positive and negative electrifications in the atmo- 

 sphere. It is well known, from the researches of 

 •I. J. Thomson and others, that ultra-violet rays 

 rt a discharging effect upon negative electrifica- 

 tion, and Brillouin has found that cold, dry ice is 

 very sensitive to this action ; in fact, about one- 

 tenth as much so as zinc. Water is not so at all. 

 Dry crystals of ice floating in an electric field 

 would become charged positively and negatively. 

 but the negative charges would escape under the 

 influence of sunlight. The air remaining an in- 

 sulator, the surrounding air becomes negatively 

 charged. When the ice crystals forming the cirrus 

 cloud moves away from this air. it bears a positive 

 charge ; and if it evaporates, the air now surround- 

 ing it becomes positively charged. When the 

 negatively charged air descends, it charges the 

 earth negatively. At sea the negatively charged 

 air, on expansion, forms negatively charged cu- 

 mulus clouds. The effects of the travel of these 

 masses of air may explain many of the phenomena 

 of storms : and the blending of the positive and 

 negative charges by night, when there has been no 

 such travel, probably accounts for auroras, luminous 

 clouds, and diffused illumination of the sky on 

 summer nights in our latitudes. 



Telephony oyer Telegraph Lines. — Various 

 methods are now being adopted whereby telephonic 

 messages can be sent over single telegraphic lines 

 simultaneously with telegraphic signalling. This 

 possibility is realised by the use of condensers, 

 interposed in the circuit in such a way that the slow 

 telegraphic impulses do not affect the rapid tele- 

 phony waves. At each station the telephone is con- 

 nected between line and earth through a condenser. 

 The telegraph instrument is connected between 

 line and earth with no condenser. The capacity 

 of the condenser used need not exceed 02 micro- 

 farad, and in place of a tin-foil -'plate " condenser 

 it is found better to nse one formed of parallel 

 insulated wires bound together on a bobbin. For 

 this purpose the wires may be 0-1 mm. diameter, 

 copper, double silk covered, each of the wires 

 having a resistance of approximately 800 ohms. 

 Plate condensers are found to transmit waves more 

 loudly but less distinctly than these wire con- 

 densers. It is, however, suggested that loudness 

 and clearness might possibly both be attained 

 by a continuation of a plate condenser and 

 a wire condenser. The Morse-key contacts are 

 made of carbon, to avoid abrupt changes of 

 current, which would affect the telephone circuit. 

 Another way of bridging the difficulty would be to 

 connect permanently a resistance bobbin between 

 the contacts of the key. When there are inter- 

 mediate telegraphic stations between the two 

 stations that are to communicate by telephone, 

 each intermediate telegraph instrument must be 

 bridged over with a condenser. So far as the 

 telephone circuit is concerned, this is equivalent 

 to cntting out the resistance of all the intermediate 

 telegraph instruments. In addition to the above, 

 each telegraph instrument, including the terminal 

 instruments, must be provided with an inductive 

 resistance of about 500 ohms, to act as a choking 

 coil for the telephonic circuits. This system is 

 applied to the fire-alarm service in Berlin, and by 

 means of a portable telephone apparatus com- 

 munication can be made with the central fire station 

 from any of the 800 fire-alarm posts. 



