670 



NATURE 



[November 3, 1923 



India. Among recent papers may be noletl two from 

 the Department of General and Organic Chemistry, 

 namely : (i) a report n|X>n caahew kernel oil by C. K. 

 Patel.'J. J. Sudlxfrough. and H. E. Watson (vol. vi, 

 part t>). I'he cashew nut is the fruit of Anacardium 

 occiUtntale. l.iim.. an evergreen tree indigenous to 

 S. and Central America, now cultivated in India. 

 The nut contains some 42 per cent, of oil, but has not 

 Iwcn nnich used as a source of oil, because of its ready 

 sale for dessert and for use in the preparation of nut 

 chocolate. (2) Hongay oil, extracted from the seeds 

 of one of the commonest of Indian trees, Pongatnia 

 glabra, Vent., is u.sed in Hindu medicine for the 

 treatment of skin diseases ; the oil has been fully 

 reportetl upon by R. D. Desai, J. J. Sudlwrough, and 

 H. E. Watson (vol. vi. part 5). From the Bio- 

 chemical Department appears a paper by Gilbert J. 

 Fowler and Talwar Dinanath (vol. vi. part 7) upon 

 the production of sugar during the ripening of the 

 fruit of Bassia longi folia. The seeds of this plant 

 are used for oil, and the authors point out, as possibly 

 of commercial significance, that, if the fruit is gathered 

 and stored a few days under suitable conditions, 

 sufficient sugar may be found in the pulp after re- 

 moval of the seeds to make this waste product avail- 

 able as a source of alcohol upon fermentation. 



Soil Acidity and Light Intensity. — In a pam- 

 phlet published by the Cambridge University Press 

 entitled " Studies in Soil Acidity — the Importance 

 of the Light Factor," Mr. J. L. Sager gives an account 

 of ecological studies carried out in the Alpine Labora- 

 tory of "La Linnaea," Valois, Switzerland. Soil 

 samples were taken near the roots of dominant plants 

 in and around the forests of a district characterised by 

 gneiss, granite, and schists. Hydrogen ion concen- 

 tration measurements were made by the colorimetric 

 method on extracts prepared by shaking the soil with 

 water and filtering after standing for thirty minutes. 

 Tables of Ph values, dominant plants and amount of 

 shade show that several plants, usually described as 

 calcicole, are not confined to the alkaline soils and also 

 bring out a correlation between soil acidity and light 

 intensity. The acidity of the soil steadily decreases 

 on passing from the deep shade of the spruce forest, 

 through the lesser shade of the larch forest, to the 

 open ; whilst the soils exposed to the scorching sun 

 at still higher altitudes above the forests are only 

 slightly acid. Cases of high acidity with high light 

 .intensity occur only where the soil is badly aerated or 

 frequently waterlogged. The author advances the 

 hypothesis that light is able to lessen the acidity of the 

 soil. 



Species-crosses in Cochlearia. — The condition 

 of polyploidy, or species with one or more extra sets 

 of chromosomes, is being found with surprising 

 frequency in plant genera. The latest case of the 

 kind is described by Mr. M. B. Crane and Miss A. E. 

 Gairdner {Journ. Genetics, vol. 13, No. 2) in species 

 of Cochlearia. They find that C. officinalis and 

 C. alpina have 28 chromosomes, C. danica 42, and 

 C. anglica 49-50, all the numbers being thus multiples 

 of 7. They have also made crosses between the 

 various species, with interesting results that are as 

 yet incomplete. The range of variation of the Fg 

 offspring is in some cases greater than the combined 

 ranges of the parents. The interesting condition is 

 disclosed that the forms with higher chromosome 

 number do not have larger nuclei, and there is some 

 indication that the higher numbers have arisen 

 through some process of fragmentation or transverse 

 fission. Further investigation will lead to a more 

 complete analysis of the changes involved. This is 

 also the beginning of a valuable and much-needed 

 increase in our knowledge of species-hybrids. 



NO. 2818, VOL. I 12] 



The Molluscan < ulptaria. — In west and 



south-west Africa ti ;iid a small but beaTjtifn! 



little genus of land <:ril.)ed by L. 1 



in 1855 under the ; ^ria. This h;i 



recently proved auutouucail) by Dr. E. I 

 {Arch. Molluskenk., iq23. No. 4) to belong to 

 the more primii "icoids, the En^ 



tida;. A con >ti of these 



which was mati<- i>y .>ir i'. iv. 1-ramcs when hcr\ing 

 with the Northern Force in the campaign in German 



South-west Africa in 1914-15, havmg b' • ' ' 



with other material in the hands of Mr. H. ' 



he has been able to give a monographic 



the genus (Ann. Natal Mus. vol. v.). Tliree new 

 species are described, briiu'iiiL' the total hd to cii'lit an<i 

 the whole are carefully 

 with excellent figures dr. I 



Standard Inductance Coils. — The Bureau of 

 Standards has Issued a leaflet giving detail«-'i mvin,, 

 tions for the construction of a series of ^ 

 inductance coils suitable for laborat(jr\ 

 The series of "inductors," 17 in nun 

 designed to cover the approximate in- 

 of 8 to 5000 microhenries. Each sucxessive cod 

 arranged in order of magnitude and beginning with 

 the smallest has 50 per cent, greater inductanc • 

 the preceding coil. Very little mechanical 

 required to make these coils. It is a real step .;. 

 advance when you can give instructions at once to .1 

 mechanical assistant to make coils of any specifieti 

 inductance. These coils in conjunction w^ith a 

 variable air condenser form a very accurate and ' 

 worthy wavemeter. Full working diagrams arr 

 and the costs for material and labour are ver> 

 To those who remember the difficulties of me.i 

 or calculating small inductances twenty year;^ .i^-. 

 the ease with which standard inductances, even those 

 which have to be used with high frequence .-nrr,.Mf 

 can now be constructed, is wonderful. 



Interferometer Experiments in AcoL^.ll 

 Gravitation. — The Carnegie Institution of W. 

 ton issues as Publication 5so. 310 a rep>ort b\ . lu. 

 Carl Barus on further expjeriments in which the inter- 

 ferometer is used for the measurement of very small 

 quantities. These are in the main a development of 

 the acoustic investigations with the pin-hole probe 

 already described in Publication No. 310, 192 1. 

 Pressure variations at a node are converted into 

 static pressures through the intervention of the 

 pin-hole and measured at a mercury U-gauge, read 

 by displacement interferometry. The pin-hole prolw 

 responds effectively to nodes in organ-pi|>es. but 

 ignores the antinodes. With a device so sensitive to 

 nodal regions the construction of a pin-hole resonator 

 suggested itself. Great difficulty was encountered 

 in the construction of the pin-hole. Both the size 

 and the slope of the walls are critical. A salient pin- 

 hole generates acoustic pressure, a re-entrant pin-hole 

 acoustic dilatation, and there is neutral behaviour 

 between the two. Within its restricted field the pin- 

 hole resonator serves admirably for the acoustic 

 survey of the interior of a room in which an organ 

 pipe is sounding. If the phenomena were visible, the 

 room would probably have the stratified appearance 

 of a vacuum-tube stimulated by electric discharge 

 For a given position of the pipe, nodal regions alter 

 nate with anti-nodal regions, quite irregular in dis 

 tribution but none the less fixed in position. An 

 account is given also of work on gra\-itation, in which 

 an endeavour is made to ascertain with what accuracy 

 the constant may be found in a self-contained 

 apparatus under ordinary laboratory- conditions. 

 The results are encouraging, but the experiments are 

 not yet completed. 



