42:2 



NATURE 



[September 3, 1903 



point noticed by Prof. Celli, who has stated that one of the 

 Italian immune areas is remarkable for an enorrnous de- 

 velopment of the cultivation of the tomato, a fruit rich in 

 vegetable acid, and an attractive food for mosquitoes. The 

 necessity of further investigation of this matter is clear, for 

 if confirmation is obtained, such knowledge may be of much 

 importance in its practical application for the prevention of 

 malaria. 



The micro-balance exhibited by Prof. Nernst at the 

 Berlin congress is described in a recent number of the 

 Berichte, and a number of results are given which illustrate 

 its remarkable sensitiveness and accuracy. The control is 

 a stretched quartz fibre, and the pointer moves over forty 

 small divisions, each of which represents oo3763mg., and 

 can be read to a twentieth part. The scale pan is a tiny 

 platinum tray weighing only 2omg., and in this the analyses 

 are carried out. Three analyses of calcite, in each of which 

 less than 3mg. was taken, gave €©2 = 43-80, 43-66, and 

 43-81 per cent., theory 43-96, and the ignition of a single 

 milligram of yttrium sulphate gave the atomic weight as 

 88-0 and 87-8, theory 89. The balance is specially suited 

 for the analysis of traces of rare earths, and an attempt was 

 made to carry out a fractional distillation of the chlorides 

 of yttrium, erbium, and ytterbium in a platinum tube, but 

 analysis showed that the sublimate had the same composi- 

 tion as the residue. Even where considerable quantities 

 of material are available, as in the analysis of the salts of 

 organic acids, the use of the micro-balance would lead to a 

 great reduction of time and trouble, as it would only be 

 necessary to read the deflection before and after igniting 

 a trace of the salt. The balance, in a portable form, is 

 manufactured by Messrs. Spindler and Hoyer, at Gottingen, 

 and is sold at 70 marks. 



Owing to the growing use of fused quartz in physical 

 and chemical experiments, considerable interest attaches 

 to determinations of the coefficient of thermal expansion of 

 this substance. Several papers on this subject are before 

 us. Messrs. L. Holborn and F. Hemming, in the Annalen 

 der Physik (4) x., find an average value for the coefficient 

 of expansion between 0° and 1000° of 5-4x10-% but con- 

 sider that the relation between length and temperature 

 cannot be adequately expressed even by a quadratic formula 

 within these limits. Mr. Karl Sheel, using optical inter- 

 ference-methods, and working with the temperatures 15°, 

 56' and 100°, obtains between these temperatures the 

 formula 



^t = 'ol I + 0'322. 10""/ + 0-00147. lO-''/^), 



while for expansion of crystalline quartz parallel to its 

 principal axis he finds 



^« = 4(i + 7"i44-iQ~"^'^ + ooo8is,io-''V2). 



In the Biillelin des Seances of the French Physical Society, 

 M. A. Dufour, in treating generally of the uses and proper- 

 ties of fused quartz, refers to the work of Holborn and 

 Hemming, Le Chatelier and Callendar, and points out the 

 difficulty of forming junctions between the quartz and metal 

 or glass, consequent on the low coefficient of dilatation of 

 the former. Mr. Sheel finds confirmation of his results in 

 a recent paper by Chappuis, who also used optical methods 

 in his determinations. 



In the July issue of the Quarterly Journal of Microscopical 

 Science, Dr. R. Evans, of the Georgetown Museum, de- 

 scribes a new species of Peripatus from British Guinea, 

 illustrated with a coloured plate. The species is said to be 

 markedly different from the other members of the group 

 from the same district. The author remarks that measure- 



ments and descriptions of colours and markings from pre- 

 served specimens are of little value in specific discrimin- 

 ation, and are, indeed, liable rather to cause confusion. 

 In the same journal Dr. G. C. Bourne describes and figures 

 a new ascidian {OUgotrema psammites), belonging to the 

 fapiily Molgulidae, dredged off New Britain. The peculi- 

 arities of the new form are twofold. Firstly, it differs in 

 general appearance and structure from the other members 

 of the group, presenting a superficial resemblance to a sea- 

 anemone. Secondly, as indicated by the occurrence of 

 small crustaceans in its interior, it has a different class of 

 nutriment. It is, in fact, " an ascidian which captures 

 and feeds on active Crustacea of large size relatively to itself, 

 and is no longer dependent on minute organisms and 

 organic debris swept into its branchial chamber by ciliary 

 currents." 



" The Building of the Grampians" is perhaps about as 

 difficult a geological subject as could be found, but thanks 

 to the labours of James Nicol, Sir A. Geikie, Prof. Lap- 

 worth, and others, much has been done, while the memoirs 

 and maps of the Geological Survey form a good basis for 

 further work and criticism. Mr. Peter Macnair has dealt 

 boldly and confidently with the subject (Royal Phil. Soc, 

 Glasgow), his object being to bring out the striking 

 similarity which exists between the structure of the 

 Grampians on the one hand and the Alps on the other, the 

 Grampians being regarded as simply the basal wreck of 

 such a mountain chain as the Alps. He is more confident 

 than others are of the succession of the rock-groups met 

 with in the Highland schists, but when he comes to 

 criticise the belt of supposed Arenig rocks along the 

 southern Highland frontier, he finds that there no reliance 

 can be placed upon the apparent order of succession. He 

 may be right in maintaining that there is nothing to justify 

 the separation of this supposed Arenig belt from the crystal- 

 lin.^ schists. He may be right also in his criticisms on the 

 structure of the Cowal region, with especial reference to 

 the development of the foliation planes. This much may 

 be said, that while hammering earnestly at the rocks, he 

 has also made a careful study of the work of others, and he 

 attacks the Highland problems with evident enthusiasm for 

 his subject. We must leave to those concerned the defence 

 of the positions which he assails, although in some instances 

 Mr. Macnair has advanced, perhaps, where others fear to 

 tread. 



Prof. Joly has done well to undertake the petrological 

 examination of paving sets. In the first part of his work 

 {Sci. Proc. Royal Dublin Soc, vol. x.. No. 5) he deals 

 more particularly with certain granites, diorites, and 

 dolerites. In his general remarks he observes that the re- 

 sistance to wear varies directly, as do the amounts of 

 quartz and felspar, the holocrystalline igneous rocks being 

 as a rule the toughest. Markedly porphyritic, vesicular, 

 and glassy rocks are to be avoided. He deals with the 

 durability and with the character of the surface produced 

 by various paving sets, remarking that mechanical forces 

 are applied on the roads in the most destructive form, the 

 attrition and crushing being combined with the solvent 

 action of impure waters. Fine-grained rocks, such as the 

 diorite of Penmaenmawr, may become too slippery for use 

 on inclined surfaces ; a certain coarseness of grain is usually 

 desirable. 



We have received the annual report (vol. xii.) of the 

 Geological Survey of Canada for 1899 (dated 1902), by Dr. 

 Robert Bell, acting director. This is a bulky work made 

 up of various independent reports lettered A to S, and 



NO. 1766, VOL. 68] 



