August 5, 1922] 



NA TURE 



iqi 



A difficulty which the economic botanist frequently 

 meets is illustrated by an inquiry (by S. T. Dunn) 

 into the cause of the variability in the' yield of 

 camphor from the Camphor tree (Cinnamomum 

 Camphora). Some trees are found to be worthless, 

 the oil yielding no solid camphor on distillation. 

 Careful examination discloses no perceptible botanical 

 difference between good and worthless trees, but there 

 may be peculiarities which affect only the chemical 

 products of the tree. Such physiological varieties 

 are known in rubber and timber trees. Investigation 

 indicates that climatic conditions, the age of the 

 leaves when cut for distillation, and the general health 

 of the tree have an important bearing on the yield. 



British and Irish Paguridea. — The Paguridea 

 (including hermit crabs and the stone crab) which have 

 been found on the coasts of Ireland had been studied 

 by Mr. C. M. Selbie, of the National Museum, 

 Dublin, who died at the Somme in July 1916. The 

 account now published (Fisheries, Ireland, Sci. Invest. 

 1921, I.) has been completed from Mr. Selbie's rough 

 drafts by Dr. S. W. Kemp. The material reported 

 upon, nearly all obtained by the Irish Fishery Cruiser, 

 contains eleven species, one of which — Nematopagurus 

 longicomis — has not hitherto been known from British 

 waters. To complete the list of British and Irish 

 representations of this tribe there are to be added an 

 Irish species of Eupagurus recorded in 1866, and two 

 species — one Diogenes and one Anapagurus — known 

 from the shores of Great Britain but not yet discovered 

 in Irish waters — a total of fourteen species. The 

 majority of the species inhabit water that is shallow 

 or of moderate depth, but one — Parapagurus pilo- 

 simanns — is a true deep-water species and occurs at 

 depths ranging from 250 to 2260 fathoms. Three of 

 the fourteen species extend north of the Arctic Circle 

 and eight are found in the Mediterranean. There are 

 keys to the families, genera, and species, and a 

 systematic account is given of each species with 

 notes on its distribution. 



The Semi-Diesel Engine. — Owing to the high 

 price of fuel in France at the present time the Mechan- 

 ical Arts Committee of the Societe d 'Encouragement 

 pour l'lndustrie nationale has thought it desirable to 

 publish an account of the present position of the 

 semi-Diesel engine, and in consequence the May issue 

 of the Bulletin of the Society contains an article of 

 nearly 100 pages on the subject from the pen of M. A. 

 Schubert. It goes into the theory of the engine, the 

 reasons which have led to its development, the forms 

 which it at present takes in France and in other 

 countries, and the oils which can be used in it. Under 

 the last head the author deals especially with the 

 vegetable oils which are produced in great quantities 

 in the French colonies in Africa and in Asia. It 

 concludes with a short account of the tests of such 

 engines carried out recently by the Society in con- 

 junction with the Automobile Club of France and 

 the marine and agricultural authorities. From the 

 results we gather that several engines of horse-powers 

 from -z\ to 50 show a consumption of oil of the order 

 of 320 grams per h.p. hour, while one of 20 to 30 h.p. 

 consumes 247 grams only. M. Schubert's article, 

 while intended primarily for French engineers, will be 

 found of great value by the engineers of this country. 



Underground Workrooms. — In the Annual Re- 

 port of the Chief Inspector of Factories for 192 1 

 special reference is made to conditions in under- 

 ground workrooms. Of the 300 rooms inspected 

 during the inquiry a number were expressly designed 

 for use as workrooms and the conditions were satis- 

 factory. But others were never intended for use in 

 this way and the structural conditions render it im- 



NO. 2753, VOL. I IO] 



possible to secure good lighting, ventilation and 

 sanitarv conditions. Of the rooms visited about 61 

 per cent, were provided with means for flushing the 

 rooms with air, in lo per cent, the through ventilation 

 was only partial, and in 19 per cent, it appeared that 

 there was practically no through ventilation. It was 

 considered that the state of the air was fresh or satis- 

 factory in 68 per cent, of the rooms, while in 24 per 

 cent, it appeared to be close or stale, and in 8 per 

 cent, stagnant. In approximately 78 per cent, of 

 the rooms the natural light was deemed insufficient 

 to light the whole of the room, but, fortunately, in 

 most cases the artificial lighting was considered satis- 

 factory in intensity although glare due to imperfectly 

 screened lamps appears to be common. There is no 

 doubt that access of light through windows is often 

 neglected ; in some cases broken windows are obscured 

 by sacking, cardboard, etc. Daylight is undoubtedly 

 superior to all but the very best artificial lighting, 

 and the effect of a mixture of daylight and artificial 

 light is rarely satisfactory. Every effort should there- 

 fore be made to secure the maximum admission of 

 natural light in underground buildings. Another 

 drawback to the use of basements as workrooms is 

 the tendency for dust to enter from the pavement 

 outside. Mention is made of a case where a trough 

 fitted under a grid ventilator at pavement level was 

 found to be filled by about a quart of black dust. 

 Muslin or gauze is sometimes fitted over ventilator- 

 entries to prevent dust entering, but the pores of the 

 material are liable to become choked and it requires 

 frequent washing. 



A Chemical Spectrometer. — A spectrometer T of 

 entirely novel design has recently been produced by 

 Messrs". Adam Hilger, Ltd., of _ 75 a Camden Road, 

 N.W.i. By the application of an autocollimating 

 telescope the designer has been enabled to dispense 

 with the collimator tube of 

 the ordinary spectrometer. 

 The arrangement of the 

 components is shown in the 

 sectional drawing, Fig. 1. 

 The eye-piece E of the tele- 

 scope contains, on the left, 

 the slit and small auto- 

 collimating prism for intro- 

 ducing the light which, 

 after passing through the 

 object glass O, proceeds to 

 the 30° prism P, is reflected 

 from the silvered back 

 surface and re - traces its 

 path through the object 

 glass to the eye-piece where 

 the spectrum is viewed. 

 The prism is rotated by 

 means of a micrometer^ 

 screw which is attached to 

 a drum D giving readings 

 direct in wave - lengths. 

 The design of the instru- 

 ment renders it extremely 

 compact. In size and ex- 

 ternal appearance it is 

 similar to a microscope and 

 occupies about the same 

 amount of table space. Fig. i. 



It has the additional ad- 

 vantage of ease in setting up, convenience in manipu- 

 lation and low cost, compared with a spectrometer 

 of the ordinary tvpe having a similar degree of 

 accuracy. Such an instrument should tend to 

 encourage the more general use of spectroscopic 

 measurements in chemical laboratories. 



