March 6, 1913" 



NATURE 



19 



owing to want of details for some countries. A 

 tabular statement gives for a number of stations for 

 which long series of observations were available the 

 normal rainfall and the percentage of years with 

 deficiency (1) between 30 and 45 per cent., (2) between 

 4^ and 60 per cent., and (3) more than 60 per cent. 

 In India places on the coast usually fare better than 

 those in the interior ; but burning sun and hot-dry 

 winds during a long break in the rains do much more 

 harm than in some other countries. In the United 

 States, e.g. a deficiency of rain produces nothing like 

 the damage that it does in India, while in Europe 

 the liability to failure in the crops is not in the least 

 comparable with that of India. In South America, 

 Brazil and the Argentine Republic show nothing 

 worse than a few cases of deficiency between 30 and 

 45 per cent., but in Chile, Santiago shows a con- 

 siderable number of cases of deficiency in the three 

 classes above mentioned ; in some parts of Chile there 

 may be a year without any rain whatever. 



The January number of the American journal Good 

 Ligliting contains an article by Prof. Gotch, of Ox- 

 ford, which gives a valuable summary of our present 

 knowledge of the properties of the eye when used for 

 detecting and observing distant coloured lights, such 

 as are seen at sea. The normal eye under such con- 

 ditions recognises a red light as red over an area of 

 the retina the radius of which is three or four times 

 that over which a green light is recognised as green. 

 Outside this area the red light is not seen at all, 

 while the green light outside its area of recognition 

 is seen as a bright white light. In view of these 

 facts, Prof. Gotch suggests that in the absence of 

 binoculars, on which in practice the recognition of 

 the colour of a distant light depends, it should be 

 noted whether the light, apart from its colour, is seen 

 better by oblique than by direct vision ; if so, it is a 

 green or white light. If it is seen better by direct 

 than by oblique vision it is red. 



Red Book No. 176 of the British Fire Prevention 

 Committee deals with tests made on a new celluloid 

 substitute, intended to reduce the risks of fire from 

 the use of kinematograph films. The material was 

 Cellit," which is an acetyl-cellulose, manufactured 

 by the Bayer Company, Ltd., and resembles celluloid 

 in all respects except that it is far less inflammable and 

 appears to be practically free from the dangers which 

 attend the use of celluloid. As the result of stringent 

 tests to which it was subjected, the material was 

 awarded the committee's certificate of "non-flaming." 

 A copy of the report can be obtained from the secre- 

 tary- of the committee, S Waterloo Place, Pall Mall, 



s.w. 



The Engineer for February 28 contains an account 

 of an automatic electric light plant manufactured by 

 Messrs. R. A. Lister and Co., Ltd., of Dursley, 

 Gloucestershire. This plant is intended for private 

 house installations, and consists of a petrol engine, 

 dynamo, automatic starting switch, and water tank, 

 the whole being mounted on two cross girders pro- 

 viding facility for setting down and removal. A 

 small battery is supplied, of capacity very much below 

 NO. 2262, VOL. 91] 



that of our ordinary private electric lighting plant. 

 When the battery is charged and no lights on, the 

 engine is at rest. If lights are switched on in number 

 below that capable of being dealt with by the normal 

 discharge of the battery, the engine remains at rest 

 until the battery voltage drops to a certain value. 

 On this voltage being reached, current is automatic- 

 ally sent through the dynamo, and runs it as a motor, 

 thus starting the engine, an operation facilitated by 

 the exhaust valve being automatically held open. 

 When the battery is sufficiently charged, the engine 

 stops again. The engine will also start and keep 

 running if the demand is higher than that which can 

 be dealt with by the battery alone. Exhaustage of 

 the battery by reason of failure of the engine to start 

 when required is prevented by a time-limit circuit- 

 breaker, which allows starting current to pass through 

 the dynamo for a limited period only. The whole 

 arrangement seems likely to minimise the troubles 

 which occur in small lighting sets owing to improper 

 handling of the batteries. 



The issue for 1912 of the "Year-Book of the Scien- 

 tific and Learned Societies of Great Britain and Ire- 

 land" has now been published by Messrs. Charles 

 Griffin and Co., Ltd. It is described on the title- 

 page as a record, compiled from official sources, of 

 the work done in science, literature, and art during 

 the session 1911-12, and in consequence its appearance 

 is a little belated, and the information provided about 

 some associations rather behind the times. But the 

 present is the twenty-ninth issue of a work of refer- 

 ence which has proved its utility to workers in science 

 and literature; its welcome would be even greater if 

 it could be published in October, when the academic 

 and scientific sessions begin. 



OUR ASTRONOMICAL COLUMN. 



Discovery of a Comet igi2d. — From The Tina's 

 of February 26, we learn that a faint comet was dis- 

 covered by Mr. B. Lowe, at Laura, South Australia, 

 on December 31, 1912. According to the report by 

 Mr. Dodwell, director of the Adelaide Observatory, 

 the object was visible in a small telescope, and was 

 seen to have a short tail; its position on December 

 30, at 5-3° P- m - (G.M.T.), was about 4 south of 

 Spica, and it was travelling southwards so rapidly 

 that the position on January 5 was about a=i4h. 

 30m., 8 = 29° 50' S. An approximate orbit gives 

 February 3 as the time of perihelion passage, when 

 the comet was probably some sixty million miles 

 from the sun, and indicates that the least distance 

 from the earth occurred about the time the object was 

 discovered, and was about twenty-five million miles. 

 Mr. Dodwell also states that Mr. Lowe anticipated 

 Mr. Gale in the discovery of comet 1910a, but did not 

 notify the fact until later. 



An Interesting Occultation.— On March 13 an 

 interesting occultation will be provided by the moon 

 passing in front of the Pleiades. As new moon 

 occurs^on March 8, our satellite will, at the time of 

 the occultation, present a fairly thin crescent, and 

 the several stars of the group will disappear at various 

 points on the dark limb, to reappear at the bright 

 limb. The first bright star to disappear will be 

 Electra (mag. = 3-8), which will enter near the southern 

 horn at ioh. im. p.m. Then will follow Merope 



