38 



NATURE 



[September io, 1914 



pleasant table fruit derived from Carica papaya, which 

 is grown in Montserrat, and serves as a source of 

 papain, a digestive ferment the demand for which is 

 rapidly growing, especially in Canada, and the United 

 States. The cultivation of rice is also being greatly 

 developed in Trinidad and British Guiana. 



In the April number of the Asirophysical Journal 

 Dr. Wali-Mohammad, of Aligarh College, India, de- 

 scribed the results of his investigation of the degree 

 of complexity of the spectral lines of aluminium, bis- 

 muth, cadmium, chromium, cobalt, copper, lead, mag- 

 nesium, manganese, silver, sodium, tin and tellurium. 

 As source of light he used a Wehnelt tube in which 

 the kathode consisted of a platinum foil covered with 

 oxides of barium and calcium, and the anode of the 

 metal to be investigated contained in a porcelain tube. 

 A potential difference of 200 volts was maintained 

 between the anode and the red hot kathode. The 

 tube was water-cooled and the pressure within it less 

 than 0-0 1 mm. of mercury. The light passed out of 

 the tube through a glass window at the top and was 

 received by a Hilger echelon grating of 35 plates. 

 The spectra were photographed on a series of plates 

 each suitable for a part of the spectrum. The author 

 found that few of the metals possessed complex lines, 

 and of those that did copper, lead, and manganese had 

 lines of similar structure. In nearly all cases the 

 structure shown by the echelon agreed with that found 

 previously by crossed Lummer plates. 



In the domain of electro-chemistry the greatest 

 commercial developments recently have been in the 

 utilisation of nitrogen from the atmosphere for the 

 manufacture of nitrogen products. It is only since 

 electrical power has been obtainable in large amount 

 at exceptionally low cost that the operations have 

 been carried out profitably on a commercial basis. 

 Probably the most interesting of the processes for the 

 fixation of atmospheric nitrogen is that in which 

 calcium carbide is employed as the medium for the 

 production of calcium cyanamide. We learn from 

 Engineering for August 28 that the Odda works in 

 Norway are now producing 85,000 tons of calcium 

 carbide and 80,000 tons of calcium cyanamide per 

 annum, a result due largely to the admirable 

 mechanical appliances in use. The electric power 

 available at Odda will soon be increased to 125,000 

 horse-power, and the carbide and cyanamide factories 

 will be further enlarged. The Nitrogen Products 

 and Carbide Company have acquired water-fall rights 

 in Norw^ay and Iceland which will enable a total of 

 about one million horse-power to be generated — suffi- 

 cient for the production of nearly two million tons of 

 cyanamide per annum. It may be noted that the use 

 of cyanamide as a fertiliser is increasing rapidly. 



The Carnegie Institution of Washington has pub- 

 lished the second volume of the "Guide to the Mate- 

 rials for American History, to 1783, In the Public 

 Record Office of Great Britain." This part contains 

 departmental and miscellaneous papers, and is by Prof. 

 C. M. Andrews, Farnam professor of American history 

 in Yale University. The scope of the work and the 

 method of treatment were explained when attention 

 NO. 2341, VOL. 94] 



was directed to the publication of the first volume. 

 The new part runs to 427 pages, and deals with papers 

 of the Admiralty, the Lord Chamberlain, Custom 

 House, Treasury, War Office, High Court of Admir- 

 alty, and other departments. 



OUR ASTRONOMICAL COLUMN. 



Comet 1913/ (Delavan). — The following short 

 ephemerls gives the positions of Delavan 's comet 

 (1913/) for the current month : — 



Greenwich Midnight. 



K. A. 



Ii. m. s. 



Dec. 



September 8 ... 9 8 35 

 16 ... 10 8 6 



+ 49 56 

 49 51 

 24 ... II 9 33 ... 47 56 



The comet is now in the constellation of Ursa Major, 

 and is not far from the two third magnitude stars k 

 and I. On clear nights It Is a conspicuous object in 

 the northern heavens, and is easily picked up from 

 the rough chart given in this column for last week. 

 It Is gradually becoming brighter, but the occurrence 

 of bright moonlight during the last week has made 

 observations somewhat difficult. 



The Recent Eclipse Expeditions. — Further news 

 Is to hand regarding some of the observers W'ho went 

 out to observe the total eclipse of the sun. The 

 Morning Post of September 3 gives some Information 

 about the party from the Royal Observatory, Green- 

 wich, through Mr. Hepburn. Mr. Hepburn accom- 

 panied this party as a volunteer assistant to Minsk, In 

 Russia, and they observed the eclipse under satisfac- 

 tory conditions. He left there on the Sunday after 

 the eclipse, but while most of the plates exposed were 

 then not developed, one that was developed showed 

 the spectrum of the chromosphere. Mr. Hepburn 

 arrived In England on September i vid Finland, Nor- 

 way, and the North Sea, and he expected the official 

 members of the party to be home on about Septem- 

 ber 6. It Is stated that the instruments will be sent 

 to the Russian Imperial Observatory at Pulkovo, 

 where Prof. Backlund, the director, has arranged to 

 keep them pending a favourable opportunity to return 

 them to Greenwich. Mr. R. C. Slater had arranged 

 to go to Riga (Russia) to make his observations, and 

 sent his instruments there direct. He found, accord- 

 ing to the Times of August 31-, that he was unable to 

 cross the Baltic. Having with him only a 4-in. lens 

 he rigged up a camera and made his observations at 

 Stromsum, In Sweden. With this he was successful, 

 and he Is recorded to have brought back with him 

 excellent photographs of the corona. 



The Mirrors of the Helw^w Khedivial Ob- 

 servatory. — Bulletin No. 12 of the Khedivial Ob- 

 servatory at Helwan is devoted to accounts of the 

 photographic tests of the figures of the new and old 

 thirty-Inch mirrors by Messrs. Walter S. Adams and 

 H. Knox-Shaw respectively. The new mirror, the 

 gift of Mr. Astor, was figured by Mr. Ritchey at 

 Pasadena, and the method of testing w^as that of 

 Hartmann. In the first tests a small amount of 

 astigmatism was indicated in the zones along the 0° 

 and 90° diameters, but none along the 45° and 135° 

 diameters, or. In other words, the figure of revolution 

 of the mirror was fairly good. A comparison of the 

 computed and observed values of the focal lengths of 

 the zones showed that the central zones were still 

 greatly undercorrected. Further work In the mirror 

 by Mr. Ritchey has greatly improved it, and a second 

 series of tests has indicated that the agreement of the 



