286 



NATURE 



\yan. 23, 1890 



was confirmed on the former of these dates by each of three 

 photographs. Two more stars have been found having a similar 

 periodicity — Aurigae and b Ophiuchi. The hydrogen lines of 

 -^Ursse Majoris appear to be broader when the K line is double 

 than when it is single. Several other lines are also seen double 

 when the K line is double. Measures of the plates gave a 

 mean separation of O'lifi millionths of a millimetre for a line 

 whose wave-length is 448'!, when the separation of the K line, 

 whose wave-length is 3937, was o'igg. 



The explanation of this phenomenon proposed by Prof. 

 Pickering is that the brighter component of this star is itself 

 a double star having components nearly equal in brightness, 

 but too close to have been separated as yet visually, and some 

 interesting results have been worked out which appear to 

 support this hypothesis. — American Journal of Science, January 

 1890. 



Spectroscopic Observations of Algol. — A note on the 

 motion of this star in line of sight has previously appeared 

 (Nature, vol. xli, p. 164). The detailed investigation of the 

 six photographs taken at Potsdam is given by Prof. Vogel in 

 Astronomische Nachrichten, No. 2947, from which the following 

 is taken. Motion towards the earth is represented by a minus 

 sign, and a motion of recession by a plus sign ; both are ex- 

 pressed in geographical miles per second : — 



Distance from 

 minimum, 

 h. 

 1 1 '4 after. 

 22*4 before. 

 19*4 before. 

 13-3 after. 

 22 '3 before. 

 1 9 "6 before. 



Motion in line 

 of sight. 



-5-0 

 + 6-9 

 + 7*5 

 -5-6 

 + 6-2 

 -f-6-8 



From these results it will be seen that, before minimum, Algol 

 has an average motion of recession of 6 '8 geographical miles 

 per second, but after minimum it approaches the earth with an 

 average velocity of 5 '3 geographical miles per second. A re- 

 duction of the measures by the method of least squares shows 

 the velocities per second to be — 



Before the minimum, -F 5 '3 geographical miles, 

 After the minimum, -6*2 ,, 



which give an average motion of recession or approach = S'7 

 ■miles. The entire system is found to be moving towards the 

 earth with a velocity of 0*5 geographical miles per second. 



GEOGRAPHICAL NOTES. 



At a meeting of the South Australian branch of the Royal 

 Geographical Society, on November i, 1889, Mr, Tietkens gave 

 an account of his recent explorations in Central Australia. His 

 expedition was despatched by the Central Australian Exploring 

 and Prospecting Association, and consisted of a party of five 

 persons, including a black tracker and a native boy. At one 

 point of his journey, when the party came within sight of " an 

 imposing range," Mr. Tietkens hoped to find a watercourse flow- 

 ing from its slopes to Lake Amadeus. He was disappointed. No 

 watercourse worth mentioning was discovered, nor any spring 

 or place where water could collect. Mr. Tietkens discovered 

 several ranges of hills, to which he gave names. One of the 

 pleasantest places found by him he called Gill's Creek, after the 

 hon. treasurer of the South Australian branch of the Royal 

 Geographical Society. Here a stream flows from a range of 

 hills through a gorge or glen of sandstone formation. " This, ' ' he 

 says, " was a most beautiful spot, where a few days could be spent 

 profitably, so the camels were unloaded, and Billy and myself 

 went up the creek to explore its wonders. We found that the 

 creek separated into three distinct channels. Following the 

 principal one, we found the creek to be running through a glen 

 with perpendicular cliffs 80 or 100 feet high on each side, and 

 fully three miles in length. We returned to our charmingly 

 situated camp late in the afternoon. . . . The water will not be 

 found to be always running, but in the glen at the head of the 

 ^reek, and which I have named after my sister Emily, large 

 deep pools will be found, four or five chains long, 10 and 15 

 feet deep, and so shaded by rocks from the sun that they cannot 

 be looked upon as otherwise than permanent." After the read- 



ing of the paper Mr. G. W. Goyder, Surveyor- General, ex- 

 pressing gratitude to Mr. Tietkens, said that although as an 

 effort to increase the extent of Australian mineral and pastoral 

 resources Mr. Tietken's expedition might have been a compara- 

 tive failure, yet the route which he had travelled might serve as 

 a most useful base for after-comers. His journey showed that 

 no large large river, as had been hoped, flowed into Lake 

 Amadeus, and only gave another proof that the interior of 

 Australia consists of a series of low mountains with shallow 

 basins, which in wet seasons form lakes and in dry seasons 

 evaporate. 



Messrs. George Philip and Son have issued an excellent 

 map showing all Stanley's explorations in Africa from 1868 to 

 1889. Each expedition is distinctly marked in colour, and dated 

 on the map ; and a condensed account of the explorer's travels 

 and discoveries is provided by Mr. E. G. Ravenstein. 



THE SOURCES OF NITROGEN IN SOILS} 



'X'HE number of this half-yearly Journal, issued last April, con- 

 tains nineteen valuable contributions, covering a considerable 

 portion of the large subject of agriculture. Many of them are of 

 purely practical import, such as the report upon the previous 

 year's prize farm competition, on implements exhibited at the 

 Nottingham meeting, and on the Exhibition of thoroughbred 

 stallions of February last. Among the articles of special 

 scientific interest may be named "The History of a Field newly 

 laid down to Permanent Grass," by Sir J. B. Lawes, F. R. S. ; 

 "Grass Experiments at Woburn," by W. Carruthers, F.R.S. ; 

 " The Composition of Milk on English Dairy Farms," by Dr. 

 Paul Veith, and the Annual Reports of the scientific staff" of the 

 Society. The Journal contains 380 closely-printed pages, is well 

 illustrated, and replete with tables and statistics. Among such 

 a mass of information, all of which possesses important economic 

 value, it is by no means easy to make a selection for special 

 notice. The changes within the soil, in the formation of a 

 meadow by Sir John Lawes, are, however, worthy of close 

 attention at a time when grazing and stock-feeding appears to 

 be the most popular remedy for the agricultural depression under 

 which the country has so long suffered. These observations are 

 also important scientifically, as they throw light upon the in- 

 teresting question as to the sources of nitrogen in all soils. The 

 gradual improvement of grass land, from the period when it is 

 first laid down until it assumes the character of old pasture, is a 

 well-known agricultural fact. The gradual increase in the 

 amount of nitrogen per acre in the meadow selected by Sir John 

 Lawes throws light upon this practical observation, and is 

 recorded as follows: — "There can be no doubt that there has 

 been a considerable accumulation of nitrogen in the surface soil 

 during the formation of the meadow (1856 to i888), amounting 

 in fact to an average of nearly 52 pounds per acre per annum over 

 the last twenty-three years. The question arises, Whence has 

 this nitrogen been derived ? " This is, as is well known, a con- 

 troverted point. The balance in favour of this acccumulation of 

 nitrogen within the soil is still large, even after every source of 

 nitrogen in fertilizers employed, foods fed upon the land by live 

 stock, rainfall, and from every other possible source is taken 

 into account. Therefore, Sir John comes to the conclusion that 

 the gain of nitrogen in the surface soil must have had its source 

 either in the subsoil, the atmosphere, or both. There is much 

 experimental evidence pointing to the conclusion that at any 

 rate some deep-rooted leguminous plants derive a considerable 

 quantity of nitrogen from the subsoil. Reasoning upon the 

 question as to how far the whole of the accumulated nitrogen in 

 the surface soil has been derived by deeply-searching roots from 

 the subsoil, Sir John says, " On this point we think it may safely 

 be concluded, from the results of the experiments of Boussingault 

 and of those made at Rothamsted, many years ago, that our 

 agricultural plants do not themselves directly assimilate the free 

 nitrogen of the air by their leaves. But in recent years the 

 question has assumed quite a new aspect. It now is. Whether 

 the free nitrogen of the atmosphere is brought into combination 

 within the soil under the influence of micro-organisms, or other 

 low forms, and so serving indirectly as a source of nitrogen to 

 plants of a higher order ? Thus Hellreigel and Wilfarth have 

 found, in experiments with various leguminous plants, that if a 



' "The Journal of the Royal Agricultural Societyof England," April 1889. 

 (John Murray, Albemarle Street.) 



