December i, 1923] 



NA TURE 



791 



of the new triplets, mentioned in the letter in Nature 

 of September 22. Again following Sommerfeld {Ann. 

 d. Physik, 70, ,32, 1923) it is concluded that in the 

 oxygen group the terms labelled by Fowler as mS 

 are single, while the mP terms are triple, and the 

 mD terms quintuple, just as in the case of chromium, 

 which is in the same column of the periodic table. 

 Accordingly the so-called " singlet " series of oxygen 

 are really of a complex nature, a fact that has already 

 been suggested by others (see Fowler, loc. cit., p. 166), 

 while in general the series spectra of the oxygen 

 group are similar to those of chromium, as far as 

 complexity of terms is concerned. 



As already noted, similar triplets were found in 

 sulphur, while independently the diagrams by 

 Brackett and Birge had been used to predict the 

 position of most of these new lines, the agreement in 

 all cases being within the limits of error. The 

 diagrams also allow the identification of some of 

 the other new lines. In particular, the diagrams 

 indicate that the triplets called, in the letter in 

 Nature of September 22, 0P-3Z) and 0P-4Z) are 

 in reality 0P-2S and oP-35 respectively, while those 

 called 0P-2S and 0P-3S remain unidentified. In 

 addition, the ^5279 narrow triplet of sulphur has been 

 identified as 1S-2P. All these points, as well as 

 more general questions, are fully discussed elsewhere 

 by one of us (Birge, " Spectral Series of Divalent 

 Elements," Jour. Opiical Society of America, now in 

 the press). One of the conclusions of that paper, 

 derived from a study of the spectral diagrams 

 already mentioned, is that the possible triple levels 

 of the oxygen group, oP and op, while having different 

 sets of inner quant numbers, running in opposite 

 directions, have nevertheless the same average 

 numerical magnitude. But for some unknown reason 

 the oP (valence) level represents a more probable 

 condition, and op does not actually exist. Similarly, 

 in the case of the elements of the second column 

 of the periodic table, the non-appearing os level 

 coincides numerically with the iS valence level. 



J. J. HOPFIELD. 



R. T. Birge. 



University of California, 



Berkeley, 



October 16. 



Identification of Pure Organic Compounds. 



In his review of Mulliken's " Identification of Pure 

 Organic Compounds," vol. iv., on p. 581 of Nature 

 of October 20, your reviewer surely does the author 

 an injustice. Perhaps he is unacquainted with the 

 earlier volumes, as I am, at present, with the latest — 

 that under review. But I can testify to the great 

 value of volumes i. and ii., and have used them 

 regularly for the last two years. In identifying the 

 components of commercial dyestuffs and similar 

 work, Mulliken's methods are far less troublesome 

 and time-expending than the classical method de- 

 scribed by your reviewer, and aptly termed by 

 Mulliken in his preface " the Method of the Empirical 

 Formula." I nave never experienced failure in 

 preparing a characteristic derivative by following 

 Mulliken's prescriptions, working with quantities of 

 about ,V gram. In fact, his beautifully neat methods 

 for manipulating small quantities deserve to be 

 more widely known, and, in my opinion, it is a matter 

 for regret that your review will prevent this. 



VV. A. Silvester, 



Research Department, 



British Dyestuffs Corporation, Ltd., 



Blackley, Manchester. 



NO. 2822, VOL. I 12] 



I WELCOME Mr. Silvester's statement, and am glad 

 to hear that Mulliken's methods are appreciated 

 and found useful in technical organic chemistry. 

 In these matters it is only possible to speak from one's 

 own experience, and, as a research organic chemist 

 and teacher of thirty years' standing, I should not 

 dream of allowing my research students to learn 

 to rely on jNIulliken's methods. I adopt this attitude, 

 not because his methods are bad or inaccurate, but 

 because they are incomplete, and an extension of 

 his system to meet all requirements would be im- 

 practicable. J- F- T. 



Amanita muscaria on Hampstead Heatii. 



The letter from Dr. O. Rosenheim in Nature of 

 October 27, p. 622, would doubtless cause astonish- 

 ment to many mycologists. Amanita muscaria is 

 one of the commonest toadstools, and is to be found 

 amongst almost any clump of birch trees in this 

 country, consequently being a common sight in woods 

 and on commons near London. The association 

 between fungus and tree, moreover, is so constant 

 that it is not unlikely that the mycelium is one of 

 those concerned in forming birch mycorrhiza. 



It is, however, the statement that there is difficulty 

 in obtaining this and presumably other common 

 agarics for scientific investigation that occasions 

 this letter. If any chemist or physiologist desire 

 such specimens, I should be pleased to circulate 

 members of the British Mycological Society to that 

 effect. That common species even are sometimes 

 not to be had has been brought forcibly to my notice 

 during the past two seasons. Lactarius vellereus 

 was asked for last year at a time when, normally, 

 the season is on the wane. Though the fungus had 

 appeared in quantity in July and August — the season 

 that year was abnormally early — it was exceedingly 

 scarce in October and November. This year, though 

 many mycologists have been on the look-out for it 

 since the beginning of the season, I have heard of 

 no one finding sufficient to fill a vasculum, let alone 

 the promised hampers; Amanita mappa, on the 

 contrary, has been so amazingly abundant every- 

 where that pantechnicons could have been loaded 

 with it. 



It should be emphasised also that toadstools have 

 their due season, the majority appearing some time 

 during the period after summer rains until autumn 

 frosts, and consequently it is not possible to provide 

 f/esh material of a given agaric all the year round. 



J. Ramsbottom. 

 British Museum (Natural History), 

 South Kensington, S.W.7, 

 November 3. 



Insecticides. 



I am interested in the question raised in Nature 

 of October 27, p. 622, as to the efficacy of camphor 

 in preventing moths, and the apparent absence of 

 experimental evidence on the subject. May I suggest 

 that the whole matter of " insecticides " needs in- 

 vestigation. Daily we see upon advertisement hoard- 

 ings the most alarming pictures, showing the truly 

 devastating effects of popular insecticides on every 

 known and unknown species of the insecta. I have 

 had an opportunity of testing the truth of these 

 statements, and I am profoundly disillusioned. 



At the beginning of the rainy season in India my 

 bungalow became in a few days infested with thousands 

 of fleas, which had hatched in the floor matting. 



