588 



SCIENCE 



[N. S. Vou LII. No. 1355 



must be observed at T by a vibration tele- 

 scope,^ in which case magnificent wave forms 

 appear, measurable in amplitude. 



2. Observations. — In the experiments, when 

 the pipe F, Fig. 2, soimded its fundamental as 

 softly as possible, the even horizontal band of 

 fringes became definitely sinuous. Probably 

 at the limit of audition there would be no 

 response, except with much larger fringes. 

 A strong fundamental makes the double am- 

 plitude about a fringe or more in width. The 

 waves of the overtone are correspondingly 

 shorter and high. The adjutages measured 

 I = 21 cm. between plates. Reducing this to 

 I = 14 cm. the fundamental came out much 

 stronger, but the loud overtone gave a more 

 confused record. Without adjutages the fun- 

 damental (Z ^ 5 cm.) still evoked very marked 

 waves, but the response of the shrill octave 

 had naturally quite vanished. Moreover the 

 form of the waves, obtained here without any 

 mechanism but with the even harmonics de- 

 leted, is of additional interest. 



3. Deductions. — Apart from details, I 

 showed in the early paper* that for a length 

 of tube I containing homogeneous air, the 

 density increment Ap for the wave-length A 

 may be written Ap^ iC/lB)n\, where C = 

 W X 1.27 is the optic constant Po(/*o — ^^o 

 and n is the total fringe displacement. Hence 

 if 



1 = 20 cm., X = 6 X 10-5 cm., p = .0013, 

 TO = 1/10, Ap/p = 1.03 X 10-3 



for the soft pipe note. Eayleigh considers 

 dp/p = 6 X 10-" just audible, so that my value 

 is of a reasonable order, holding about 2.4 X lO-' 

 times more energy per average cm.' (p dp/p = 

 10' ergs/cm.') than Rayleigh's limiting note. 

 For the shorter adjutages the main energy 

 would be correspondingly larger. An open 

 cylindrical resonator close to an equipitched 

 open organ pipe can just be seen to respond. 

 Blown at its edges by a lamella of air, how- 

 ever, strong waves antedate the first audible 

 sibillation of pitch. Into the variety of inter- 



3 Carnegie Publ. No. 249, III., Chap. V.; IV., 

 Chap. VI., 1919. 

 4C. P., 149, p. 145. 



esting stroboscopic effects I can not enter 

 here . Carl Barus 



Bkown Univebsity, 



PROVmENCE, E. I. 



THE AMERICAN CHEMICAL SOCIETY 



( Continued) 

 A mosaic disease of cabbage as revealed by its 

 nitrogen constituents: S. L. Jodidi, S. C. Moijlton 

 and K. S. Marklet. The cabbage disease investi- 

 gated is characterized by denitrifieation taking 

 place in the affected tissues, whereby the nitrates 

 are in part reduced to ammonia which is lost as 

 such, and in part to nitrites which reacting on the 

 amino groups of the various organic compounds 

 — acid amides, amino acids^ etc. — ^bring about the 

 elimination of elementary nitrogen. This is the 

 reason why diseased cabbage tissues have a smaller 

 proportion of total, nitrate, acid amide, diamino 

 and monoamine nitrogen, nitrites occurring in dis- 

 eased tissues only. Denitrifieation occurs in af- 

 fected cabbage leaves in a very much higher de- 

 gree than it does in the roots. There is a higher 

 proportion of protein in the diseased cabbage tis- 

 sues than in the normal. Loss of nitrogen in the 

 affected cabbage tissues is in itself an explanation 

 of the cabbage disease. Thus, e.g., one of its 

 conspicuous characteristics, the dwarfing of the 

 plants, is easily understood when we bear in mind 

 that the nitrogenous compounds such as acid 

 amides, amino acids and others, which are partly 

 lost through denitrifieation, are the very materials 

 out of which the plant is building up its tissues. 

 In the healthy cabbage samples the nitrogen is 

 made up, in round figures, of 30 per cent, protein 

 nitrogen, 7 per cent, diamino nitrogen, 10 per cent, 

 mono-amino nitrogen, and 13 per cent, peptide ni- 

 trogen, which means that at least 13 per cent, of 

 the nitrogen compounds present in cabbage have 

 direct nutritive value. 



The influence of the diet of the cow upon the fat 

 soluble and water soluble vitamine of cow's miXk: 

 R. Adams Dutcher, Cornelia Kennedy and C. 

 H. EcKLES. Albino rats were fed purified diets 

 containing casein, dextrin, agar, butter fat, wheat 

 embryo extract and an adequate salt mixture. 

 Varying quantities of winter milk and spring milk 

 were fed with diets containing no added butter 

 fat and with other diets containing no embryo ex- 

 tract. It was found that spring milk is superior 

 growth-promoting properties with regard to both 

 the fat soluble and the water soluble vitamine. 



