August 28, 19 19] 



NATURE 



513 



In the Times of August 15 there is an account 

 of an excursion to the forests of Belgium under the 

 guidance of M. H. Vendelmans, an expert in land 

 reclamation. The historic forest of Soignes has not 

 been seriously injured by the Germans, who were 

 induced by M. Crahay, Director of Forests, to accept 

 double the normal output, about 650,000 cubic ft. of 

 timber in all annually. Promiscuous felling was 

 thus avoided, and the forest retains its former 

 aspect, to all appearances unimpaired. During the 

 war some valuable researches were carried out by 

 the Belgian foresters. The ravages of the fungus 

 {Peridermium strobi) which had stopped the plantmg 

 of the valuable white pine have been arrested by 

 the spraying of the seedlings. Ash seed gathered 

 early and sown immediately, e.g. on August 16, has 

 been found to germinate fredy in the following 

 season, while seed gathered in October and sown 

 in spring does not come up until the second year. 

 This discovery of hastening the germination of ash, 

 hawthorn, etc., which "lie over" ordinarily for a 

 season, is not new, but has seldom been acted upon, 

 as foresters feared that early gathered seed, bemg 

 immature, would produce feeble seedlings. Worth- 

 less sandv tracks in the Campine are successfully 

 afforested' after preliminary cultivation, mainly with 

 yellow lupine, 'which adds humus to the soil. 

 Japanese larch and Sitka spruce have proved very 

 successful in such soil, being as valuable speaes in 

 Belgium as they are in England. 



The fundamental importance of a knowledge of 

 the properties of the refractory materials used in 

 hic^h-temperature furnaces has been for some time 

 recognised by the United States Government, and 

 the Bureau of Standards has for the last two or 

 three years been engaged in researches on the sub- 

 ject The quartz or ganister bricks used for furnace 

 work in the States are made mainly in Pennsylvania 

 from crushed and ground quartzite rock. About 

 2< per cent, of lime is added, and the mixture 

 moulded in steel moulds, dried and burnt in kilns 

 at 25oo°-3ooo° F. The best procedure to be fol- 

 lowed in these processes, and the effects of varia- 

 tions of the procedure, are discussed in Technologic 

 Paper No. 116 of the Bureau by Mr. D. W Ross, 

 and the effects of repeated burnings on the con- 

 stitution and microstructure of the bricks by Messrs. 

 H Insley and A. A. Klein in No. 124. It appears 

 that the quartz is converted on heating into cristo- 

 balite and tridvmite, which are both of lovyer 

 densitv. Unless' this conversion is completed during 

 the original burning, the resulting brick will expand 

 on further heating, with serious results to the 

 structures of which they form a part. 



The June issue of the Proceedings of the National 

 Academy of Sciences of the United States contains a 

 paper on the temperature of the human skin by 

 Messrs. F. G. Benedict and W. R. Miles and Miss 

 A Johnson which throws a considerable amount of 

 light on the conduction of heat from the interior of 

 the human body to the skin. One^ of the most 

 instructive of the observations made is that of the 

 temperature of different points on the skin of a nude 

 person exposed for 2^ hours to a temperature of 

 146° C. While the internal temperature remained 

 76-7*^ C, the temperature of the skin became high up 

 on the chest 295°, at the nipple 22°, at the waist 30 , 

 groin 24°, knee 22°, ankle 21°, shoulder 29°, and 

 buttock 21°. A person clothed in the usual way has 

 skin temperatures which differ from each other by 

 c° C. onlv, the chest and waist being hottest (34 ^.), 

 the buttock and calf coldest (29° C). The skin tem- 

 peratures were taken by means of a copper constantan 

 NO. 2600, VOL. 103] 



couple in series with a string galvanometer giving a 

 photographic record as the junction was moved slowly 

 over the skin. 



Messrs. Ilford, Ltd., have recently introduced 

 what they call "photographic vision" (or P.V.) colour- 

 filters for use in connection with their various plates. 

 Each transmits just that light to which the plate that 

 it matches is sensitive, so that by looking at any 

 object through either of them the colours of the object 

 will appear of the same relative tone-values as they 

 will be represented if photographed by the plate with 

 which the filter corresponds. The improvement that 

 will be effected by the use of colour-sensitive or pan- 

 chromatic plates can thus be easily investigated. By 

 adding to the " P.V." filter any colour-filter available 

 for use in conjunction with the plate, the effect of 

 photographing on the given plate and using the given 

 colour-filter is seen at once, so that by trying one after 

 another it is possible to find the colour-filter as well as 

 the plate that will best give the desired result. The 

 convenience of such a method of selecting plates and 

 colour-filters is obvious, e^ecially, perhaps, with 

 artificially coloured objects, such as pictures and 

 stained sections in photomicrography, though this 

 method of trial must be of advantage in all photo- 

 graphy except where pure black-and-white is con- 

 cerned. An account of these with " micro-filters," 

 other colour-filters, and the nature and use^ of their 

 colour-sensitised, and especially panchromatic, jjlates 

 will be found in a pamphlet entitled " Panchromatism " 

 that has just been issued by Messrs. Ilford, Ltd. The ■ 

 pamphlet is illustrated with many examples that show 

 the advantages of panchromatic plates in scientific, 

 commercial, and pictorial photography, and gives 

 technical details as to exposure and development that 

 will very much facilitate the use of them and of the 

 colour-filters. 



A recent issue of the Organiser contains a special 

 section dealing with industrial lighting. An article 

 by Mr. Leon Gaster summarises the advantages of 

 good illumination from the point of view of health, 

 freedom from accidents, and efficiency of work, and 

 quotations are made from the report of the Depart- 

 mental Committee on Lighting in Factories and 

 Workshops in order to indicate the main principles 

 to be- complied with. Artificial lighting is also dealt 

 with in an article by Mr. H. C. Wheat on the 

 lighting of machine-shops. The author attaches 

 importance to the use of gas-filled lamps on the 

 overhead system of lighting, and some effective illus- 

 trations of this method are shown. The modern 

 tendency is strongly towards general lighting^ of this 

 type, which leaves the room clear, enables lights to 

 be well out of the range of vision, and permits re- 

 arrangement of machinery without the necessity of 

 disturbing the lighting system. Mr. E. G. W. 

 Soustei* deals with natural lighting in factories. It 

 is not too much to say that the shape of a modem 

 factory is determined mainly by access of daylight. 

 Expenditure in this direction is fully justified, both 

 by its direct influence on work and by the fact of its 

 enabling an economy to be made in the use of 

 artificial light. 



Messrs. H. K. Lewis and Co., Ltd., 136 Gower 

 Street, W.C.i, have sent us their July list of 

 additions to their medical and scientific library during 

 the months April-June. The catalogue is one that 

 should be of interest and service to all readers of 

 Nature desirous of keeping abreast of scientific 

 literature, giving, as it does, particulars of all 

 important books dealing with the sciences published 

 recentiy in this country and the United States. The 

 list will be sent free to any address upon application. 



