September 21, 1911] 



NATURE 



393 



No. -'. vol. xxxiv., of The Astrophysical Journal, Dr. Joel 

 ns discusses the probability of there being a number 

 of readily detectable eclipsing variables among those stars 

 known to be short-period spectroscopic binaries. Such 

 st:irs must offer the phenomena of mutual eclipse to some 

 of the universe, and Dr. Stebbins establishes the 

 probability that a very fair proportion will present more 

 or less partial eclipses to the earth; as a class, that is, 

 offer greater probability of the discovery of eclipsing 

 variables than do the bulk of the stars. Not only that, 

 but their periods can be more or less determined from 

 their spectroscopic elements, and so the times of maximum 

 light-variations suggested. Such periods would be the 

 mosl favourable for observation, and with the selenium 

 photometer Dr. Stebbins considers that for stars of magni- 

 tude 20 and brighter a o-io magnitude variation may be 

 considered conspicuous, so that very small eclipses might 

 evident in properly timed observations. 



To test his proposition. Dr. Stebbins made observations 

 of Auriga; and 5 Orionis, and found that both were 

 eclipsing variables. The work on the latter is not yet 

 complete, but its extreme light-range is not far from 

 o.io magnitude. 



In the case of B Auriga;, a number of consecutive 

 observations indicated no change, but on October 23, 1910, 

 the selenium photometer showed the magnitude to bi 

 0.07 fainter than before. From a number of observa- 

 tions, fully discussed in the same number of the journal. 

 Dr. Stebbins finds that the total range is 00S7 magnitude, 

 of which 0-076 is due to eclipses and o-on is due to 

 ellipticitv of figure of the two components. The times of 

 light-minimum are apparently in exact accordance with 

 the times predicted from Baker's spectroscopic elements. 

 It would also appear that the surface-intensities of the 

 components are many times greater than that of the sun. 



Cometary Phenomena. — From Dr. K. Bohlin we have 

 received an abstract from the Naturwissenschaftlichen 

 Rundschau in which he reviews our present knowledge 

 of cometary phenomena. In the first part systems of 

 comets are dealt with, and in the last of five well-defined 

 systems, we find comet 1910a classed with 1890 IV. and 

 IQ07 I. In dealing with the light, extent, and structure 

 of comets, there is little that is new to record ; and in 

 the chapter on spectra the latest results are not mentioned, 

 although they replace much that preceded them. The 

 section discussing the tails of comets, and the strange 

 fluctuations in the streams of matter forming them, is 

 interesting, and is illustrated by some reproductions from 

 photographs. 



Observations and Catalogues of Nebulae. — Now that 

 the subject of the classification and distribution of nebula; 

 is to the fore, Dr. Bauschinger's publication in vol. iv., 

 part i., of the Annalen der Kaiserlichen Universitais- 

 Sternwarte in Strassburg, of the Strassburg observations 

 and catalogue, will prove a welcome addition to the litera- 

 ture dealing with the subject. 



The publication consists of three parts, in the first of 

 which Dr. Wirtz discusses his observations of nebula; made 

 with the 49-cm. refractor during the period April, 1902, to 

 March, 1910. The general methods of observation are 

 described, and then the results tabulated; special micro- 

 meter measures of the stars in the Omega and Dumbell 

 nebulae were made, and the results are shown on two 

 charts. 



The second part of the present publication contains a 

 il catalogue of the nebula; observed at Strassburg 

 from 1881 until 10 to, and gives the various designations, 

 the positions (19000), and brief descriptions of the physical 

 features of 1257 nebula; ; the catalogue has been compiled 

 by Dr. Wirtz. who writes the introduction, wherein he 

 points out that it is the outcome of the work initiated 

 by Winnecke in [872. The final part of the publication 

 consists of a most interesting comparison, bv Dr. Wirtz. 

 of the Strassburg results with those of other nebula- 

 observers. 



A New Orsf,ry\tory in Africa. — From No. 4510 of the 

 Astronomische Nachrichten we learn that the French Geo- 

 graphical Society charged M. Jarry Desloges with the 



erection of a more or less temporary observatory on the 

 " Hautes Plateaux " of northern Africa. Extensive and 

 arduous researches as to the " seeing " at various places 

 over a wide region at an altitude of 1100 metres or more 

 have been made, and now an observatory is in course of 

 erection. 



RECENT SOIL INVESTIGATIONS. 

 TT is well known that the United States Bureau of Soils 

 does not attach the same importance to a chemical 

 analysis of the soil as is usual elsewhere. The argument 

 adopted is that all soils contain the same rock minerals, 

 and therefore the soil solution from which plants derive 

 their nourishment must be identical in composition, so far 

 as mineral plant food is concerned, in all cases. But 

 inasmuch as the aqueous extracts of different soils show 

 the same kind of differences towards plants as the soils 

 themselves, it follows, if the original hypothesis is true, 

 that the infertility of the poor soils must be due to some 

 toxic organic substance. Search is therefore being made 

 for substances of this nature, and during the progress of 

 the experiments numerous interesting fields are opening up. 

 Evidence has, for example, been obtained which is con- 

 sidered to prove that the roots of growing plants, and par- 

 ticularly the root hairs, possess an extracellular oxidising 

 power ; this power is greatest in fertile soils, and is 

 diminished in certain infertile soils. The oxidation is 

 attributed mainly, if not entirely, to the activity of a 

 peroxidase produced by the roots. Messrs. Schreiner and 

 Reed, the authors of this paper, also consider that soil 

 itself can effect oxidations closely analogous to those of an 

 oxidase, although, in their view, the process is mainly 

 non-enzymotic. 



Another publication, also from the Bureau of Soils, gives 

 the results of Messrs. Robinson and McCaughey's investiga- 

 tions on the colours of soils, which they trace to organic 

 matter and to ferric oxide. All varieties of colour, from 

 white to yellow, red, brown, and black, are thus derived, 

 the darker colours indicating, as a rule, the better agri- 

 cultural conditions. 



In addition to the research work going on, the Bureau 

 of Soils is also engaged in a soil survey of the States, the 

 results of which are issued in the form of circulars dealing 

 with particular soil types. The basis of the survey is the 

 mechanical analysis of the soil ; but the officer in charge 

 makes full local investigations, so that the report always 

 takes account of the agricultural conditions. Among the 

 reports issued, so far, are those dealing with the Ports- 

 mouth sandy loam, the Sassafras silt loam, the Norfolk 

 fine sandy loam, and the Norfolk fine sand. In a general 

 introductory circular Dr. Whitney describes in non-technical 

 language the kind of examination that is made in the 

 laboratory, and the limitations to which soil analysis is 

 subjected. The account is very interesting, and will be 

 found useful to others engaged in this work. 



Messrs. Hart and Peterson, of the Wisconsin Agricultural 

 Experiment Station, have recently published their work on 

 the sulphur requirements of farm crops. Some years ago 

 Mr. Dymond directed attention to the problem here, and 

 showed that the supply of sulphates was not always 

 adequate to the needs of the crop. A similar conclusion is 

 reached by Messrs. Hart and Peterson, and they suggest 

 that, in order to meet the losses due to drainage and 

 cropping, it will be necessary for permanent fertility to 

 supply sulphates to the soil. 



The biochemical significance of phosphorus is discussed 

 by Miss Caird in a paper read before the Royal Society of 

 Victoria, a reprint of which was recently to hand. The 

 low phosphorus content of the Australian soils is well 

 known ; it appears, also, that Australian native grasses 

 have a markedly lower phosphorus content than European, 

 and that the wood of Australian trees is lower in phosphates 

 than European trees. Acclimatised European grasses con- 

 tain more phosphorus than the native sorts, but less than 

 the same kinds grown in Europe. Finally, it is pointed 

 out that the loss of phosphorus from Virtorian grass lands 

 by export of their products is considerable, and must be 

 made good. 



NO. 2 186, VOL. 8/] 



