690 



NATURE 



[July 29, 1920 



very interesting experiments of his own, and con- 

 cludes that in the "most highly sensitive photo- 

 graphic plates we are dealing with crystalline silver 

 bromide in which, besides gelatine, some highly un- 

 stable form of colloidal silver exists in solid solution, 

 and thai it is this dissolved silver which first under- 

 goes change on exposure to light.'' He finds a 

 reasonable explanation of solarisation "by assuming 

 a peptising action on the part of the later-formed 

 chemical products of light action (bromine, hydro- 

 bromic acid, etc.) with formation of a photohalide 

 relatively rich in dissolved silver, but almost un- 

 developable." 



A NEW radio call signal used by the Post Office is 

 described by Major Shaughnessy in the Electrical 

 Review for July i6. Until recently one of the draw- 

 backs to radio reception was that it was always neces- 

 sary for an operator to be listening, as there was no 

 method of making the received signals operate a loud 

 calling device. There are many outlying small radio 

 stations in this country in islands and lightships the 

 number of calls on which is so small that it would 

 not justify the expense of having an operator always 

 in attendance. The Post Office, by using a simple 

 valve amplifier, a Turner thermionic relay, and a 

 retardation device in series, has successfully em- 

 ployed the weak radio currents to ring a bell. In 

 order to call the station a long "dash" of 15 seconds 

 duration is sent. During this time a condenser at 

 the receiving station is slowly charged through a 

 3-megohm resistance. After about twelve seconds 

 the condenser is practically fully charged, so that 

 when the signal ceases and the tongue of the relay 

 ■^ moves back to the spacing stop the discharge of the 

 condenser deflects a second relay, and this causes a 

 bell to ring. This condenser device has been used by 

 the Post Office for several years on land lines to call 

 the operators, and is found to be very efficient. Trials 

 of the set have proved that it is practically impossible 

 for "jamming" or atmospheric disturbances to 

 actuate the apparatus. It has been fitted on the 

 P.O. cable ship Monarch, and even with heavy 

 "jamming" has proved successful up to a hundred 

 miles. This calling device can be applied for sending 

 the distress signal at sea known as the S.O.S. signal. 

 It will obviously extend the use of radio communica- 

 tion to much smaller ships than at present, as the 

 saving of operators' wages considerably reduces the 

 cost of maintenance. 



Two recent articles in the Engineer (July 2 and 9) 

 describe at some length the hydro-electric power works 

 at the Great Lake, Tasmania, which is situated 

 approximately at the geographical centre of the island 

 at an altitude of 3350 ft. above sea-level. From the 

 southern end of the lake the River Shannon finds an 

 outlet some two miles west of the bed of the River 

 Ouse, and the two streams flow in fairly parallel 

 courses for some distance. But the fall of the River 

 Ouse is much more rapid than that of the River 

 Shannon, with the result that, while at a point 

 opposite the middle of the lake the Ouse has an 

 elevation of 120 ft. above it, a few miles south the 

 NO. 2648, VOL. 105] 



Ouse has fallen to considerably rtiore than 1000 ft. 

 below the Shannon, A shdrt 'connection between the 

 two rivers at this point enables a very high head of 

 water to be obtained. ' For the initial installation only 

 the water from the Great Lake catchment area has 

 been utilised, but it is now in contemplation to divert 

 the head-waters of the Ouse into the lake, and by 

 this means a total capacity of 70,000 h.p.. will be 

 available at the turbine shafts. The dam across the 

 southern end of the Great Lake, which at present 

 impounds the water to a height of 1 1 ft. above the 

 sill, will be raised to give an effective height of 40 ft. 

 The existing power station at Waddamana contains 

 two 5000-h.p. and two 8ooo-h.p. turbines, all of 

 the Boving type ; three more 8000-h.p. machines 

 are under construction, and will shortly be installed. 

 In order to develop the total fall a second station 

 will be formed at a higher level, where a head of 

 250 ft. is available and a serviceable capacity of 

 12,000 h.p. is at present running to waste. 



We notice that, in consequence of the continued 

 increased cost of production, the published price to 

 non-fellows of the society of the Journal of the Royal 

 Society of Arts has been raised to is. 



Messrs. R. and J. Beck, Ltd., 68 Cornhill, London, 

 E.G. 3, inform us that they have obtained a supply of 

 mounted specimens of the scales of the Test Podura, 

 Lepidocyrtis curvicollis, which is recognised as being 

 one of the best tests of high-power microscope object- 

 glasses. These scales have been for long unobtain- 

 able, and the new supply will be welcomed by many 

 microscopists. 



The research on automobile steels carried out by 

 the research committee of the Institution of Auto- 

 mobile Engineers has now been brought to a success- 

 ful conclusion. It is hoped that the report, which 

 was approved at a meeting held on July 21, will be 

 ready for issue by about the end of August, when a 

 further announcement in regard to price, etc., will 

 be made. 



The "Rough List " (No. 359) of books on natural 

 history just issued by Messrs. Bernard Quaritch, 

 Ltd., II Grafton Street, W.i, will be of interest 

 to collectors of first and rare editions, for among the 

 thousand or so volumes offered for sale are many 

 treasures. There is also a good sprinkling of ordinary 

 editions listed at low prices. Practically the whole 

 ground of natural history is covered by the cata- 

 logue ; there are, besides, sections on mathematics, 

 mineralogy, palaeontology, and physics. 



A BULLETIN issued by the Department of Industries, 

 Madras, entitled "The Manufacture of Glue in the 

 Tropics from Tannery Refuse," was noticed in 

 Nature of February 5 last, p. 611. The director of 

 the Department now informs us that the pamphlet 

 has been placed on the market so that the informa- 

 tion contained in it may be widely known. The 

 pamphlet is priced at i rupee, and copies can be pur- 

 chased from the Superintendent, Government Press, 

 Mount Road Branch, Madras. 



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