514 



NATURE 



[April 2, 1908 



matter, it was not until the closing of the seas to 

 France during the wars of the Directory that the 

 necessity of an internal supply of nitrates directed the 

 attention of the French savants to the process of 

 nitrification. Their labours reduced to a system the 

 making of nitric beds, but the maximum production 

 was never more than about 5 kilos, of nitre per metre 

 cube after the bed had been established for two years. 



It was nearly eighty years later that the researches 

 of Schloesing and Miintz, Warington and Winograd- 

 skv showed that nitrification was brought about by 

 bacteria, and at the same time afforded a justification 

 and an explanation of the procedure which had been 

 worked out empirically for the nitre bed. The dis- 

 covery of the nitrate of soda deposits in Chile left no 

 place for the old nitre beds, but as MM. Miintz and 

 Lain^ point out in a very interesting memoir lately 

 presented to the Soci6t6 d'Encouragement pour I'ln- 

 dustrie natlonale (T. cix., pp. 951-1042. Paris, 

 1907), the conditions that prevailed at the close 

 of the eighteenth century might recur, and France 

 be again driven to manufacture her war stores of 

 nitrates at home. The authors have therefore been 

 studying in detail the process of nitrification on a large 

 scale to ascertain if the process could be so quickened 

 and intensified as to have any practical value. Start- 

 ing with sulphate of ammonia as a home product 

 obtainable on a large scale, they worked out the con- 

 ditions of temperature, concentration, nature of 

 medium, &c., which would result in the maximum 

 formation of nitrates. The most important step they 

 have made is to show that humus, so far from being 

 inhibitive of nitrification, as most organic substances 

 are, is actually favourable, so that peat or turf, which 

 is almost wholly humus, by reason of its great water- 

 absorbing powers and the large surface it offers, be- 

 comes the best of all substrata for nitrification, if it is 

 also supplied with a sufficiency of carbonate of lime, 

 and a vigorous growth of the necessary organisms 

 is first established in it. 



As a final result of their investigations, MM. Miintz 

 and Lain^ show that the optimum production of 

 nitrates is attained when the ammoniacal liquids per- 

 colate through successive beds prepared of finely 

 divided peat mixed with carbonate of lime. It is im- 

 possible to begin with a concentrated solution of the 

 sulphate of ammonia, 7^5 grams per litre being about 

 the optimum when the " nitriere " is in full activity; 

 but after this liquid has been nitrified, successive addi- 

 tions of fresh sulphate of ammonia can be made, and 

 the liquid put through another bed until a concentra- 

 tion of 47 grams of calcium nitrate per litre is reached, 

 a figure which is still well below the limit of 20 per 

 cent, at which nitrification ceases. With such an 

 installation the authors expect a daily formation of 

 7'5 kilos, of nitrate of calcium per metre cube of turf, 

 which represents an extraordinary advance upon the 

 old nitre beds producing 5 kilos, of potassium nitrate 

 per metre cube in two years. 



Of course, the process at present is not within the 

 domain of practical politics ; ammoniacal nitrogen has 

 practically the same market value as the nitric nitro- 

 gen produced, so that the labour expended and the 

 cost of evaporating the final solution would all be 

 wasted ; but, as the authors began by pointing out, the 

 occasion may yet arise when a country without com- 

 mand of the sea may require to manufacture its own 

 nitrates. Then " nitrieres " could be established by 

 a peat bog to convert into nitrates the ammonia which 

 could be distilled out of the peat. The only doubt 

 that occurs to us is what opening the recent electrical 

 methods of making nitrates from atmospheric nitro- 

 gen will even then leave for such a process. 



A. D. H. 

 NO. 2005, '^'^I- 77] 



PROMINENCE AND CORONAL STRUCTURE.' 



ANYONE who has studied the forms of the 

 corona observed at different eclipses knows 

 that these forms change from time to time, going 

 through phases which are more or less repeated 

 every eleven or twelve years according to the solar 

 activity. I have previously indicated (Monthly 

 Notices, R.A.S., vol. Ixiii., No. 8, p. 4S1) that there 

 is reason to believe that these changes of shape 

 depend, not on sun-spot action, but on the position 

 and percentage frequency of solar prominences, so 

 that when prominences are most frequent, cither near 

 the solar poles or equator, the coronal streamers 

 follow suit. 



Prominences can now be observed and photo- 

 graphed every day, but coronal streamers and 

 the lower corona can only as yet be seen 

 during eclipses. From photographs taken during 

 eclipses, it is difficult always to associate certain 

 streamers with prominences, and indeed this 

 should be the case. The reason for this is 

 that prominences are only seen on the limb of the 

 sun that is in profile in such photographs, while 

 streamers may be observed in perspective in addition. 

 The base of a large streamer need not necessarily, 

 therefore, be situated on the solar limb. 



It is, I think, now generally acknowledged that 

 a study of eclipse photographs has shown that there 

 is an intimate association (a) between streamers and 

 the lower corona, and (b) between the lower corona 

 and prominences. The more, therefore, tlie form of 

 the lower corona can be attributed to prominence 

 action the more the streamers will depend on 

 prominence activity. 



In the eclipses of 1898, 1901, and 1905 " arched " 

 or " envelope " structures were photographed. Thus 

 Prof. Dyson, in describing the series of tliree arches 

 he photographed in igoi, said, " A very remarkable 

 arch in the corona. Round the prominence three 

 separate arches are shown, one inside the otlier. . . . 

 Tliey have the appearance of cloud over an erup- 

 tion." 



Again, the .Astronomer Royal, referring to his 

 photographs of the 1905 eclipse, writes, "very 

 bright prominence associated with oval rings and 

 arched structure in the corona." 



The question arises, are these " arched " forms 

 composed of prominence or coronal material? Photo- 

 graphs taken with prismatic cameras during these 

 eclipses might answer this question, since they are 

 capable of recording, in monochromatic light, images 

 of the sun's surroundings. 



An examination of such photographs taken by 

 the Solar Physics Observatory's expedition had, 

 however, shown no indication of any such " arch " 

 systems, but it is quite possible that the comparative 

 faintness of the objects in question and the insuffi- 

 cient lengths of exposure given may account for 

 their absence in the records. 



So far as I am aware, no such series of " arches " 

 has been photographed except during the eclipses 

 above mentioned, so that whether the material com- 

 posing the arches is " coronal " or " prominence " 

 is still undecided. 



Although the routine work with the spectro- 

 heliograph ot the Solar Physics Observatory since 

 the year 1904 has been to secure, daily if possible, 

 photographs of the sun's disc and limb in the wave- 

 length of the " K " line of calcium, it was not until 

 July 17 of last year that a photograph w-as obtained 

 which presented a magnificent series of "arches." 



1 Abstract of a paper read before the Royal Society on January i6 (Roy. 

 Soc. Proc, Series A, vol. Ixxx., No. A 537, pp. 178-183). 



1 



