June 6, 1907] 



NA TURE 



141 



xpericnce with theoretical knowledge is the most desirable 

 nethod of producing young men qualified to take up 

 esponsible positions. 



The first annual conference of the Association of Teachers 

 1 Technical Institutions was held at the University of 

 ^eeds on May 22 and 23. The president, Mr. \. .\. 

 Vlundella, of the Northern Polytechnic Institute, London, 

 iccupied the chair, and about one hundred delegates were 

 jresent. Mr. Graham, secretary for higher education in 

 ■^eeds, said that one of the great ditliculties from an 

 .ducational point of view, especially where it is wished 

 o give students an all-round view of their particular call- 

 ing, is that of the technical teacher teaching a bread-and- 

 butter subject. If teachers could be convinced that it 

 is absolutely necessary that the pupils should understand 

 •he scientific principles underlying that subject and get ;^n 

 ill-round view of their particular trade, and not one 

 particular little picture of it, a very great service would be 

 done to technical education. In his presidential address, 

 Mr. Mundella directed attention to the great leakage 

 .-epresented by the passing outside the pale of educa- 

 tional effort of children beyond the age of twelve, and 

 he urged that up to the age of seventeen secondary 

 education, widely diversified to meet local conditions, 

 the standing of pupils, and the wishes of parents, 

 should be made compulsory. There would thus be a per- 

 fectl; -''ural development of the child. .Scholarships, he 

 said, not meet the requirements, and grammar schools 



and lie schools have no effect on the problem of 



seconc 1 education, w^hich is the provision of suitable 

 school; for the 600,000 children who leave the present 

 element ry schools. The examination system for scholar- 

 ships is undamentally wrong, besides being very expensive. 

 It works out for the w'hole country at about 20/. per 

 scholar on the average, a sum almost twice as great as 

 would maintain the child in a provided secondary school 

 belonging to the local authority. Mr. H. .^. Clark, 

 head of the engineering department of the Northern 

 Polytechnic Institute, read a paper entitled " Notes of an 

 Educational Visit to the United States." He referred to 

 the brotherly feeling between English and .American men 

 of science, and described his journey through the .States 

 and the various institutions visited. Mr. Barker North, 

 chairman of the West Yorkshire branch of the association. 

 read a paper on the preliminary training of technical 

 students. He condemned the preliminary traini"g of 

 students entering technical colleges as very inefficient, this 

 being in the main due to the desire of educational com- 

 mittees to secure large classes, paving inadequate atte^i- 

 tion to the training of the students, and unmindful of the 

 fact that it was better to produce six highly-trained men 

 than six dozen inefl^cientlv trained. .A paner by Mr. J. 

 Fitzgerald, of the .Soulh-Western Polytechiic Institute. 

 and Mr. E. L. Bates, of the London County Council School 

 of Building, Brixton, on syllabus and examinations as 

 aoplied to building subjects, was read by Mr. Bates. .At 

 the outset Mr. Bates referred to the impossibility of ore 

 individual becoming proficient in more than one craft. He 

 also dealt with the best course of technical instruction for 

 the craftsman and the general foreman. Several dis- 

 cussions of an instructive kind followed the reading of 

 papers. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society. F-bruarv 14. — "On the Specific In- 

 ductive Capacity of a Sample of Highly Purified .Selenion." 

 By O. U. Vonwiller and \V. H. Mason. Communicated 

 by Prof. Threlfall, F.R.S. 



The paper contains an account of the application of 

 methods of measurement described by Pollock and \'on- 

 willer {Phil. Mag., June, 1902) to the determination of the 

 specific inductive capacity of selenion. Two methods were 

 employed, one an absolute electrometer method employing 

 forces of a frequency of about fifty per second, and the 

 other a resonance method employing electric oscillations 

 of a frequency of 24 millions per second, which is believed 



NO. 1962, VOL. 75] 



to be more accurate than anv high-frequencv method 

 hitherto employed. The selenion was cast into' the form 

 of a plate, 15 cm. diameter and i cm. thick, this plate 

 bemg cast m such a manner as to ensure its being in the 

 vitreous condition, after which it was ground with 

 carborundum powder until the surfaces were flat and 

 parallel. .After each set of measurements the plate was 

 broken up into small pieces, and the density of these pieces 

 compared with that of the plate as a whole! 



The following results were obtained : — 



Density at I3°.8 C, 429. 



Specific inductive capacity— by electrometer method, 

 0-13 at 16° C. ; by oscillation method, 6-14 at 23''.6 C. 



Specific resistance in the dark, approximate— between 

 2-2 X 10" ohms at 20° C. and b-j x 10'' ohms at 25° C. 



Resistance measurements were made in the dark, and it 

 was noticed that the specific resistance fell considerably 

 m the light as in the case of the conducting variety of 

 selenion. 



It was found that a thin reddish film forms on the 

 surface of the selenion, though it is only exposed to air, 

 and the comparatively high conductivity "of this film gave 

 considerable trouble before it was discovered. 



February 28. — " The Enzymes associated with the 

 Cyanogenetic Glucoside Phaseolunatin in Flax, Cassava, 

 and the Lima Bean." By Prof. V\'. R. Dunstan, F.R.S.' 

 Drs. T. .A. Henry and S. J. .M. Auld. 



The authors show there is reason to believe that these 

 three plants, flax, cassava, and the lima bean, contain a 

 mixture of the two glucosidolytic enzvmes, emulsin and 

 maltase. 



The same authors had previously proved that the pro- 

 duction of prussic acid from the lima bean, cassava roots, 

 and the seeds or embryo plants of flax is due to the 

 decomposition of the cyanogenetic glucoside, phaseolunatin 

 (a-dextrose ether of acetone cyanohydrin), contained in 

 each of these plants, by an enzyme which resolves this 

 substance into acetone, dextrose, and prussic acid (Proc. 

 Roy. Soc, 1902, l.\xii., 285; 1906, Ixxviii., 145; and 

 .Inn. Chim. Pliys., 1907 [viii.], 10, ii8j. 



Since the mixture of enzymes obtained in the usual 

 manner from any one of these three plants decomposes 

 phaseolunatin and amygdalin, the characteristic glucoside 

 of bitter almonds, whilst the enzyme which occurs with 

 amygdalin in the almond decomposes amygdalin, but not 

 phaseolunatin, it seemed clear that flax, cassava, and the 

 lima bean must contain either a mixture of emulsin, with 

 some other enzyme capable of hydrolysing phaseolunatin, 

 or a new enzyme having the properly of decomposing both 

 glucosides. 



Fischer's generalisation that the glucosidolytic enzymes 

 so far systematically examined are divisible into two- 

 classes, the one capable of decomposing the o-alkvl ethers 

 of the hexoses and the other the stereoisomeric i3-alUyr 

 ethers of these sugars, has rendered it possible to classify 

 an unknown glucosidolytic enzyme by ascertaining whether 

 it is active towards the o-alkyi ethers of the hexoses or 

 towards the stereoisomeric ethers, and E. F. Armstrong 

 has extended Fischer's work in this direction by showing 

 that when the a-alkyl ethers of the hexoses are hvdrolvsed 

 by enzymes of the maltase type the sugars immediately- 

 liberated are the a-forms, and that similarly the stereo- 

 isomeric /3-elhers on hydrolysis by appropriate enzymes 

 furnish the 3-forms of the hexoses. 



These methods have been applied to the investigation 

 of the mi.xture of enzymes contained in these three plants 

 and to the determination of the nature of the dextrose 

 residue in phaseolunatin. 



It was found that the mixture of enzymes has the 

 property of hydrolysing amygdalin and salicin, which are 

 Ixjih known to be i8-glucosidcs, and similarly it decom- 

 poses a-methvl glucoside and maltase, which both have 

 the o-structure. 



Further, phaseolunatin is decomposed by yeast maltase 

 and by the mixture of enzymes occurring with it in the 

 three plants already named, yielding, in the first instance, 

 the o-form of dextrose, so that it must be regarded as an 

 o-dextrose ether of acetonecyanohydrin. .Accepting Fischer's 

 generalisation, it seems clear from these data that flax, 

 cassava, and the lima bean contain at least two glucosido- 



