December ii, 1919] 



NATURE 



379 



shows are in grave danger of speedy extermination. A 

 diving petrel is one of these, the penguin another. 

 The first-named is liilled remorselessly for food, the 

 other for the sake of its oil and feathers. .\s an 

 example of what may be done by judicious protection, 

 .Mr. Coker quotes the case of the south island of the 

 Chinchas, where the birds were left undisturbed for 

 three years. At the end of that time 22,337 t""-^ "f 

 guano were collected. 



With the October issue the Scottish Journal of 

 Agriculture completes its second volume. The con- 

 tents are varied and interesting. The first article, 

 "Problems of .'\nimal-breeding," points out the essen- 

 tial factors and principles involved, and pleads for 

 commercial utility as the real end in view. The 

 second article, on " .Aberdeen-.Xngus Cattle," is pre- 

 sumablv the first of a scries on " Scottish Pure-bred 

 Livestock." Both serve as reminders that home- 

 grown beef, as well as home-grown wheat, should find 

 a place in anv sound agricultural policy. The articles 

 on '" Rhizoctonia Disease, or Stem-rot, on Potatoes" 

 and '' Nose»ia iipis in Hive-bees" are of the l<;ind that 

 bring home to the farmer the realisation of the way 

 in which science can minister to his needs and solve 

 manv of the problems that puzzle and perplex him 

 and cause him financial loss. "Agriculture in the 

 Outer Hebrides" affords an interesting glimpse of the 

 state of the industrv in this remote and little-known 

 "corner" of the British Isles. It is not altogether 

 without significance to read that although the spraying 

 of potatoes is a firmly established custom in parts 

 of I.ewis, yet the next advance recommended is the 

 enclosing of the arable land, thereby bringing about a 

 substantial increa.se in all crops and rendering proper 

 rotations practicable. Other articles are " Oat-growing 

 Experiments in .Scotland," "Composition of Linseed 

 Recovered from Home-grown Flax," " Scottish Farm 

 Labour," ' Woodlands and Woodland Industries in 

 Relation to Small Holdings," and short notes on 

 various subjects such as " Leaf-stripe of Barley," 

 "Village Industries," " .Vgricultural Labour in Other 

 Countries," and that ever-important and intricate 

 problem " F.irm Bookkeeping and Cost .Accounting." 



The difficulties appertaining to work done in order 

 to ascertain the changes in chemical composition 

 undergone by fruits during ripening and storage are 

 enhanced by the fact that the fruit-juice may, and 

 generally does, varv in composition with Ihe method 

 of extraction. In the Biochemical Journal for Novem- 

 ber Mis.ses D. Haynes and H. M. Judd describe cx- 

 ])eriments made to ascertain whether the first runnings 

 obtained from pressed apples after freezing are similar 

 in composition to tho.se obtained later. A uniform 

 s.implc of a])ple-pulp was divided into two portions, 

 one of which w;is immediately frozen in liquid air 

 and pressed so soon as it had re-attained the labora- 

 tory temperature, whilst the other was left overnight 

 in a freezing mixture and then treated in the same 

 way. The chemical and physical properties of the 

 two juices were almost identical, thus showing that 

 no more chemical action takes place in the prolonged 

 freezing of an ordinary freezing mixture than in liquid 

 air. In another series of experiments the juice was 

 expressed from apple-pulp in .several fractions to ascer- 

 tain whether the tissues after fr«>zing are freely per- 

 meable to all those constituents of the cell-sap present 

 in the expressed juice. It was found that the con- 

 lentration of acids and sugars is the same in the first 

 fraction as in "the last, but the viscosity of the latter 

 is greater than that of the former, indicating that the 

 colloidal constituents of the sap are held back by the 

 tissues. The authors find that the large fluctuations 

 in the samples investigated cause the probable error 

 NO. 2615, VOL. 104] 



to be \'ery large, and the) point out that neglect of 

 sampling errors by previous estimations made bv other 

 workers detracts very seriouslx from the v.ilue of the 

 results obtained. 



.So.viE notes on the use of the aeroplane in .Vfrican 

 exploration by Lieut. L. VX'almsley in the Geographical 

 Journal for November (vol. liv.. No. 5) are valuable in 

 giving the results of e.xperience. .Mr. Walmsley points 

 out that "air-pockets" are normally encountered 

 during the daytime in tropical .Africa up to a height 

 of about 6000 ft. -As a result he had to do his aerial 

 photography in East .Africa in the morning and 

 evening, when the light was not very favourable. 

 .\bove 7000 ft., however, he thinks that operations 

 could be carried out all day long. .As regards the 

 location of air-photographs on the map, Mr. Walmsley 

 points out that two adjoining photographs should 

 overlap, showing at least two objects in common. 

 Owing to the absence of definite objects in hundreds 

 of square miles of .Xfrican landscape, the onlv satis- 

 factory method is to operate along clearly marked 

 geographical features, such as rivers, mountain 

 ranges, and roads, so that each picture contains part 

 of an easily recognisable feature. Mr. Walmsley made 

 most successful photographic surveys in north-western 

 Portuguese East .Africa. He suggests the application 

 of photographic survey to navigable estuaries, such as 

 those of the Rufiji, Rovuma, or Ziimbezi. The shift- 

 ing mud-banks can be seen distinctlv at a height of 

 2000 ft. 



.Mr. p. R. Burchall gives an "Elementary Survey 

 of the. Present Position of .\erial Photogrammetrv " 

 in the British Journal of Photography for Novem- 

 l)er 28. .After giving many details, he concludes by 

 stating that many thoughtless people imagine that 

 aerial photographs are all that is required for map- 

 making, while many surveyors rather disdain them. 

 " Meanwhile, inventors are busy improving air- 

 craft and photogrammetric apparatus, and mathe- 

 maticians are busy working out and simplifving 

 .systems of correction." He prophesies that as soon as 

 the cheapness and accuracv of the aerial photographic 

 method have been demonstrated, it will be speedily 

 recognised and appreciated. 



TilK principal results obtained by Mr. H. J. 

 Hodsman and PrOf. Cobb in their tests of the expan- 

 sions of refractory materials were described at the 

 meeting of the Society of Glass Technology held at 

 the I'niversity of Sheffield on November 10. On first 

 firing, silica refractories are permanentiv expanded, 

 while fireclay refractories are permanently contracted. 

 On subsequent reheating both expand, and on cooling 

 contract to their dimensions after firing. It is this 

 t\pe of reversible expansion which has been inves- 

 tigated for a number of materials between 15° C. 

 and 1000° C. Kaolin, carborundum, alumina, <ilun- 

 dum, and ball-clay expand at rates which are nearly 

 constant throughout this range. Silica expands up to 

 ^00° C. at a rate slightly greater than that of kaolin, 

 between 500° C. and 600° C. at a much greater rate, 

 while l)etween 600° C. and i<x)o° C. there is prac- 

 tically no expansion. -At 1000° C. its total expansion 

 is nearly equal to that of kaolin. .A mixture of 

 ganister and cla\ containing 80 per cent, of ganister 

 expands like silica, while fireclay and pot-day h.ave 

 expansion curves which lie between those of silica and 

 kaolin, nearer to the former than to the latter. 



TiiK Times Engineering Supplement for November 

 directs attention to the announcement that 'advantage 

 is to be taken of the refitting of the White Star liner 

 Olympia for mercantile service to equip her for the 

 use of oil-fuel, and gives this fact in evidence of the 



