438 



NA TURE 



[June 9, 1910 



It is now more than twenty years since Profs. Hertz 

 and Halhvachs showed that when a metal plate charged 

 with negative electricity and insulated is illuminated by 

 ultra-violet light it loses its charge, and the rate of loss 

 under standard conditions decreases with time. To the 

 latter effect the title " photo-electric fatigue " was given. 

 It was thought bj' some to be due to oxidation of the 

 surface, by others to the direct action of the impinging 

 light. Although Hallwachs disproved both these views six 

 years ago, a considerable amount of work has been done 

 recently by experimenters, who apparently still approach 

 the subject from the point of view of the direct action of 

 light, e.g. Dr. Aigner, of Vienna, Dr. Allen, of London, 

 and, according to the Resume des Communications of 

 the Soci^t^ fran^aise de Physique for May 6, M. Eugene 

 Bloch, of Paris. All doubt as to the possibility of the 

 incident light being the direct cause of the fatigue appears 

 now removed by the experiments of Dr. Ullmann 

 (Annalen der Physik, 1910, No. 6), who has traced it in 

 the case of both copper and zinc to the formation of ozone 

 in the air surrounding the plate by the passage of the 

 light through it. 



Messrs. F. Davidson and Co., 29 Great Portland 

 Street, W., have given us an opportunity of examining the 

 thermo-generator — a new form of the old thermopile — of 

 which they are the agents for England and the colonies. 

 The thermo-electromotive-force is produced by copper- 

 antimony couples, fifty of these couples being connected in 

 series. Each couple consists of a vertical, hollow, cylin- 

 drical copper tube, to the top of which is soldered a flat 

 strip of antimony, which passes horizontally inwards and 

 then downwards around a block of a porcelain-like sub- 

 stance. The copper tubes are arranged in two parallel 

 rows of twenty-five each, and the antimony strips approach 

 one another at the top. These strips are heated by means 

 of a horizontal burner running the whole length of the 

 apparatus immediately beneath the antimony strips. Gas 

 or methylated spirit vapour is used for producing a number 

 of jets, and the heat is retained in the white blocks which 

 are in close contact with the antimony strips. An electro- 

 motive force of about 4 volts is obtained, and this is 

 sufficient to illuminate a small lamp for medical or other 

 purposes, or to run a small model lathe or fan. A total 

 current of 3 amperes can be obtained through a galvano- 

 meter provided there be no appreciable external resistance. 

 Less than one minute is required to heat the apparatus 

 sufficiently to give its full yield. A slight deposit of oxide 

 forms upon the surface of the antimony in the course of 

 time, and requires to be removed by running a stick 

 lightly between the rows while the apparatus is hot ; other- 

 wise it appears to give no trouble whatever. The thermo- 

 generator may be used for hours continuously, and takes 

 the place of dry batteries for running small illuminating 

 lamps. 



Sir William White contributes an interesting article on 

 marine steam turbines to the Engineer for May 27. In 

 reference to the excessive complication which has been 

 charged against the Parsons type, and the greater simplicity 

 credited in some quarters to the German arrangements, the 

 author points out that, after large experience in the great 

 Cunarders and in sw'iit armoured cruisers, no serious prac- 

 tical difficulty has been experienced with Parsons turbines. 

 Their advantages in regard to economy of steam consump- 

 tion, greater ease of handling the engines, and smaller 

 individual weights to be lifted when opening out turbines, 

 have been proved to be considerable. Sir William is con- 

 vinced that, on the whole, the Parsons type of turbine still i 

 maintains its superiority for marine purposes ; but he is ' 

 NO. 2 1 19, VOL. 83] 



also of opinion that neither it nor any other type will 

 secure universal adoption or be absolutely the best suited 

 for all the varied cases which occur in practice. 



An account of the trials of the Brazilian battleship Si'w 

 Paulo appears in Engineering for June 3. This ship is 

 the product of Sir W. G. Armstrong, Whitworth and Co. 

 and Messrs. Vickers, Sons and Maxim. The full speed on 

 trial — 21-623 knots — was realised with 28,645 indicat-^d 

 horse-power, while the guarantee was for 21 knots. Of 

 special interest are the gunnery trials, which took place on 

 June I off the Clyde. A complete broadside of eleven 

 4-7-inch guns was fired simultaneously with a broadside 

 of ten 12-inch guns, establishing a record in the way of 

 broadsides. Admiral Bacellar, the president of the 

 Brazilian Naval Commission, pressed the firing key w-hich 

 fired this tremendous broadside ; every one of the twenty- 

 one guns responded. Excellent practice was also made 

 at a target. Another important feature was the firing of 

 two 12-inch guns in an upper turret, laid horizontally and 

 fore-and-aft directly over a lower turret. Several Brazilian 

 and two British officers remained in the lower turret 

 during this test, and were able to state that they were rot 

 inconvenienced by any concussion. The ship is fitted with 

 an electrical firing s3-stem, which renders it quite impossible 

 to fire any gun in a position which is dangerous to any 

 other gun or any ship's fitting. 



We have received from Mr. E. Merck, of Darmstadt (and 

 16 Jewry Street, E.C.), his catalogue of chemical prepara- 

 tions for April, 1910. The list is remarkably complete 

 and it would be difficult to name any preparation requires 

 for general laboratory use which is not included. Man} 

 additions have been made to the last list, especially ir 

 therapeutical and bacteriological preparations. 



The current number of the Bulletin of the Soci6t< 

 d'Encouragement pour 1 'Industrie nationale (April, 1910 

 contains a very readable and interesting paper by Capt 

 Nicolardot on the rare earths and incandescent lighting 

 The pioneer work of Auer is described in detail, togethe 

 with the history of the search for ceria and thoria, an< 

 an account given, with illustrations from photographs, 

 the manufacture of a mantle, starting with the quarryin; 

 of the monazite sand, and finishing with the burning ol 

 and fixing the mantle. The chief types of burner ar 

 also figured and described, including the latest forms c 

 inverted burner. 



A catalogue of the first eight hundred negatives mad 

 by the Geological Survey to illustrate subjects of geologicj 

 interest, and of which prints or lantern slides are supplie 

 at a fixed tariff, has just been published by the Board c 

 Agriculture and Fisheries. The districts included lie chiefl 

 in Cornwall and Devonshire, South Wales, and the countie 

 of Cardiganshire, Derbyshire, Leicestershire, and Nottinf 

 hamshire. Copies of the catalogue may be obtained froi 

 any agents for the sale of Ordnance Survey maps, C 

 directly or through any bookseller from the Ordnanc 

 Survey office, Southampton, price 6d. each. 



Messrs. Heynes Mathew, Ltd., of Cape Town, hi 

 sent us a copy of a very complete illustrated catalogue i 

 scientific apparatus, pure chemicals, and reagents. 

 Hot shows strikingly the improvement which has tai 

 place in recent years in the supply of apparatus 

 material for scientific work in distant parts of the Empii 

 Messrs. Mathew have established a depot in Cape Tow 

 where a full range of laboratory requisites can be obtair 

 from stock. That they find it worth while to do this '| 

 suggestive testimony to the growth of science teaching 

 South African schools and colleges. 



