206 



NATURE 



[August i i, 1923 



each case, tlic i^ride o-o5o-o"ooi mm. waj5 selectrd jiiul 

 examined midn the microscope, the particles In int^ 



Discovery of A8co<li|)(( 



Ml III ( 'cs I ritl . 



\\ 1-1 .' I I 1 II '. 



Ml'' .III I. II I- i\|ii 

 III w .1 1 I lins (Iclci nil! 



a iiuiiiIm I III ((iinniuii minerals. 



I Ik ( (iiidit ions of comminution seem, however, not 

 ([iiitc ( iiiii])ar.il)lc with tho'^c in n;itnr;d soil -material, 

 when- It nia\ In- d(nil)lcil il (|iiarl/. and garnet, for 

 example, present so large a surface in comparison 

 with other minerals as appears from the table on p. 9. 

 Limouitc, again, is probably distributed in soils in a 

 m\i( li liner form than is suggested by the artificially 

 crushed material. Where a mineral grain, again, goes 

 to pieces mainly under chemical action, as in the case 

 of olivine set free from basalt, it may yield surviving 

 cores that are of considerable coarseness. The table 

 referred to, however, has obviously very great 

 interest in connexion with the work of Hendrick and 

 Newlands on the mineral constitution of various 

 grades in a fine earth. 



The American absorption-tests have been made 

 with a dye (malachite green), water vapour, and 

 ammonia, according to methods that are carefully 

 stated. Four typical samples from the U.S. soil- 

 series were then treated, and it was found that the 

 absorption by the " non-colloidal minerals " (I should 

 prefer to write " non-colloidal mineral particles ") is 

 less than 2 per cent, of the total absorption by the 

 fine earths used. It is pointed out that this result is 

 affected to some extent by the wide range of absorptive 

 power shown by the tests on separate minerals. 

 Reference is made to W. O. Robinson's work on 

 " The inorganic composition of some important 

 American soils " (U.S. Depart. Agric. Bulletin 122, 

 1914), in which the average constitution of the 

 " silt " group in 26 soils was determined as quartz 51, 

 potash felspars 7, muscovite 7, and other minerals 35 

 per cent. The dye-absorption is practically nothing 

 for quartz and orthoclase ; but the authors of Bulletin 

 1 1 22 state that in a soil rich in muscovite the 

 absorption by non-colloidal particles may be as high 

 as 7 to 20 per cent, of the total absorption of the 

 fine earth. 



The conclusion is that the particles styled colloidal 

 possess absorptive characters that are dependent on 

 their composition and not merely on their fineness of 

 comminution. The authors confirmed this opinion 

 by grinding six selected minerals dry in a steel ball 

 mill to a fineness of i micron and less, so as to reduce 

 them to the " colloidal " grade. The coarser particles 

 were then (p. 14) removed by sedimentation extending 

 over several days. The average value for absorption 

 of ammonia by these finely powdered minerals is only 

 22 per cent, of that given by the " ultra clays " from 

 a number of different soils. The fine quartz and 

 microcline showed practically no absorption for 

 malachite green ; but chlorite and muscovite gave 

 results equal to the lowest of those obtained from the 

 colloidal particles in the 33 soils tested. It is pointed 

 out that some alteration may have taken place in 

 the powdered minerals by hydrolysis during the 

 process of separation. Their absorptive power may 

 have been thus increased, and may be in part due to 

 the formation of gels upon the particles. Experiments 

 were then made with synthetic gels, and it now seems 

 highly probable that by far the greater part of 

 absorption in the fine earth of soils is due to gels in 

 the material finer than i micron in diameter. The 

 term " colloidal " thus comes to have a more definite 

 significance when applied to the constituents of a soil. 



Grenville a. J. Cole. 



Geological Survey of Ireland, 

 Dublin, July 12. 



Hitherto the species oi tins peculiar genus of 

 Streblidae have been known onK from the Malayan 

 sub r't;i')n ThanUs lo the inti-rest taken on my 

 beliall 1-v Mr. W. W. A. I'liillips (jf St. George Estate, 

 Matugania, ui 11 known locally as an authority on the 

 Chiroptera, i have to announce the di.scovefy of an 

 encysted female of the genus in the small leaf-nosed 

 bat of < e\ Ion, Hipposiderus atratus. The specimen 

 was attached to the skin in the vicinity of the tail, 

 whereas previously discovered specimens have been 

 found either in the wing membrane (Adensamer) or 

 at the base of the ear (Muir). The host, also, is of 

 a species 111 which these parasites have not l>een 

 hitherto recorded, and Mr. Phillips informs me that 

 it is usually very free from all such, a character which 

 it shares with the rest of its family. 



The identity of the specimen has b^en confirmed 

 by Mrs. Q. Cattell Kessell, working uith 1 t. Scott at 

 Cambridge. 



RON.M.I) Sl.MOK-Wni I K. 



The Kepitigalla Rubber Estates, Ltd., 



Suduganga Estate, Matale, 



Ceylon, June i. 



NO. 2806, VOL. I I 2] 



AscoDiPTERON is one of the most remarkable 

 examples of specialisation to a parasitic existence 

 known among insects. It was described by Adensamer 

 in 1896 from a single example found imbedded in the 

 dorsal wing-membrane of a bat {F^hyllorhina sp.) from 

 the Dutch East Indies. Subsequently Mr. Frederick 

 Muir found a number of examples of another species, 

 imbedded in the skin at the base of the ear, on 

 seventeen speciinens of Miniopterus schreibersi taken 

 at Amboina ; from these he obtained puparia and 

 bred both sexes of the fly, publishing an account of 

 the life-history (1912) and referring the insedt to the 

 family Streblidae. 



The newly emerged males and females have fully 

 developed wings and legs. At a later stage the 

 female bores its way into the skin of the bat by the 

 aid of a series of remarkable cutting blades on its 

 proboscis, loses its wings and legs almost entirely 

 (only the stumps being present in the fully imbedded 

 individual), and becomes almost completely encysted 

 under the skin of the host, only the posterior ex- 

 tremity of the abdomen remaining external. The 

 front part of the abdomen becomes enlarged and 

 completely engulfs the head and thorax, which come 

 to lie, as though invaginated, at the bottom of a pit. 

 The imbedded female gives birth to a full-fed larva, 

 which falls to the ground and immediately pupates, 

 as is normal in " pupiparous " Diptera. 



The discovery of specimens, which may possibly 

 represent a new species of the genus, in Ceylon is 

 highly interesting. 



Hugh Scott. 



University Museum of Zoology, 

 Cambridge, July 11. 



Antarctic Geophysics. 



Having been responsible for the final values of 

 g derived from the pendulum observations made in 

 the Antarctic in 1902-3 by Commander Bernacchi 

 and his associate Engineer-Commander Skelton, I 

 wish to direct attention to a point which has ap- 

 parently escaped your reviewer when making the 

 following statements (Nature, vol. iii, p. 898) : "The 

 mean value of g from the three pendulums used in 



