698 



NATURE 



[July 28, 192 1 



chamber. The upper glass plate of the expansion 

 chamber, through which the tracks are observed or 

 photographed, is covered on the inside with a gelatine 

 film, which is made conducting. This film is charged 

 negatively with reference to the metal piston, but 

 by means of the commutator L, which rotates with 

 the driving crank, the plate is discharged just before 

 the occurrence of the cloud formation. In the same 

 way as the expansion ratio can be adjusted while the 

 instrument is running-, so the length of the period 

 during which the electric field is cut off can also be 

 adjusted while the instrument is running- by means 

 of the screw P, which traverses the contact brush 

 along' the commutator L, which is shaped, as will 

 clearly be seen in the illustration, in the manner re- 

 quired to give this adjustment. Also rotating with 

 the crank are two adjustable lead seg-ments, M and N, 

 which can be used as shutters for admitting X-rays to 

 the expansion chamber at the proper intervals. It is 

 on the back of the disc carrying* these segments that 

 the commutator L, above described, is fitted. 



The expansion chamber is fitted with a small tube, 

 by means of which radio-active matter can be intro- 

 duced into the chamber for the production of o- or 

 jS-rays. The present chamber is made 55 mm. in 

 diameter, which is, of course, less than the length 

 of the tracks "of some of the o-rays in air, but the 



velocity of the a-rays can be reduced by passing them 

 through a mica screen. A small screen can also be 

 placed on the piston to cut off the a-rays, except at 

 the moment of greatest expansion. The expansion 

 chamber must be perfectly airtight, as the minutest 

 lag produces eddy currents, which at once destroy the 

 tracks. The instrument is very quicklv set up and 

 easily operated, as a few expansions serve to filter out 

 any dust originally in the air. The piston forming the 

 floor of the expansion chamber is covered with a 

 comparatively thick layer of gelatine containing about 

 10 per cent, of Indian ink. This gives a good black 

 background, against which the tracks show up bril- 

 liantly. For demonstration purposes a Pointolite lamp 

 gives excellent results, but for photography a rather 

 more brilliant lamp is desirable. The apparatus is 

 illuminated by means of a parallel beam of light 

 coming in on the left-hand side. The screen R cuts 

 off all light, except a small rectangular nencil passing 

 through the middle of the expansion chamber. 



Mr. Shimizu has taken some stereoscopic pictures on 

 kinematograph film with his original apparatus, and 

 by means of these stereoscopic pictures the exact paths 

 of the particles in space can be calculated. The Cam. 

 bridge and Paul Instrument Co., Ltd., hopes shortly 

 to bring out a suitable stereoscopic camera as an 

 accessory to the expansion apparatus. 



Scientific and other Aspects of Beer. 



ADRIAN BROWN, the first professof of the first 

 established university school of brewing in this 

 country, died nearly two years ago, and no one more 

 suitable than Prof. Armstrong could have been chosen 

 to pay a tribute to his memory.' Prof. Armstrong's 

 enthusiasm for the application of chemistry to biology 

 is undimmed by age; his memories and friendships 

 reach back further than most men's, and (may it be 

 added in a scientific journal?) he has a fine apprecia- 

 tion of the glories of beer. He feels he has observed 

 what would have been Adrian Brown's wish, in 

 making his eulogy be "less of the man than of the 

 veast-cdl," more of the school than of the teacher. 

 After some biographical details and personal reminis- 

 cences going back to the 'sixties, he discusses Adrian 

 Brown's scientific work, placing that on the barley- 

 corn first. There is a variety with a blue layer of 

 cells underlying the thin outer skin of the corn ; the 

 blue colouring matter behaves like litmus, and is 

 turned red bv acids ; yet when the grains are soaked 

 in dilute acid thev remain blue, for only water enters. 

 This discovery enabled Adrian Brown to study a semi- 

 permeable membrane in a living object and to examine 

 the behaviour of a large number of substances towards 

 it. Water is absorbed from a saturated salt solution, 

 but the more dilute the solution the more rapidly is 

 water taken up. Sugar, strong acids, and strong 

 alkalis also give up the water in which they are dis- 

 solved without entering themselves. On the other 

 hand, weak acids, also weak bases, such as ammonia, 

 and chemicallv neutral substances, like alcohol and 

 chloroform, readily pass through the membrane. 

 Prof. Armstrong suggests that only the simple 

 "hvdrone" molecules of water, which alone are con- 

 sidered bv him to have the formula H,0, penetrate 

 the membrane; complexes like H.O. and H,0, are 

 held back. Cane-sugar is held back by the membrane 

 of the barleycorn, yet it passes through the walls of 

 the yeast-cell ! 



1 Adrian Tirown Memorial Lecture, "The Particulate Nature of Enzymic 

 and Z' mic Change." By fTenry E. Armstronjr. Delivered at Birmingham 

 University on February' i8. (Journ. Inst, of Brewing, 1921, vol. xxvii., 

 pp. 197-160.) 



Brown's investigation of the oxidative action of 

 Mycoderma aceti and B. xylinum leads Prof. Arm- 

 strong to an account of Bertrand's work on the bac- 

 terial oxidation of sugars ; similarly his researches on 

 enzymes lead to a review of older and newer work 

 on heterogeneous catalysis, the kinetics of enzyme 

 action, and the mechanism of alcoholic fermentation. 



But chemists who know the lecturer and are already 

 more or less acquainted with the ground he covers 

 will turn with the greatest interest to the section on 

 " Beer as a Dietetic." Fortified by quotations from 

 Calverley and from Prof. Saintsbury's recent " Notes 

 on a Cellar-Book," he inveighs against State regula- 

 tion of the brewing industry and against prohibi- 

 tionists. It may have been stern necessity, but 

 Government control has rendered beer " little short of 

 worthless as a drink." Lord D'Abernon's committee 

 does not escape, and is accused of verbal quibbling in 

 its report. "The most malign of the attempts to 

 influence opinion is probably that of the Board of 

 Education, in the form of the syllabus of * Lessons on 

 the Hygiene of Food and Drink for Use in Schools 

 and Notes for the Assistance of Teachers,' issued over 

 the name of Sir George Newman." Later Prof. 

 Armstrong calls out : " Is all aesthetic pleasure to be 

 taken out of life? Are we to treat our food with the 

 contempt we show to the coal we cast upon the fire? 

 Are the views of an entirely selfish, unthinking 

 minority to prevail?". And then comes his answer: 

 " No, I believe our philosophy to be summed up in 

 the familiar lines : — 



Man wants b't little here b-'ow. 

 But likes that little good." 



After this we go back once rn're to science, to a 

 historical review of the science of brewing. The debt 

 we owe to Pasteur is sympathetically explained to a 

 general audience, but those who are already acquainted 

 with the work of the great Frenchman will perhaps 

 learn most from the survey of the "Burton period' 

 and the author's reminiscences of Henry Bottinger, 

 Horace and Adrian Brown, Peter Griess, and O 'Sul- 

 livan. This chapter in the history of English chemis- 



NO. 2700, VOL. 107] 



