August 5, 1904.] 



SCIENCE. 



179 



of the hexamethylene ring. ' Dextro ' and 

 ' Isevo ' menthone are shown to be not true 

 optical isomens. Several other cases of rota- 

 tion change were noted, and found to be due 

 in general to chemical alteration of the 

 nucleus. 



The author emphasized the value of geo- 

 metric formula, and especially a modification 

 of the Kekule-Baeyer tetrahedral models, and 

 showed that certain plane formulae, which have 

 been seriously discussed, are impossible of 

 construction by the models, and must be con- 

 sidered as, at least, improbable. 

 The Determination of Formaldehyde: E. H. 



Williams. 



The author gave the results of a critical 

 study of four of the more commonly used 

 methods for the determination of formalde- 

 hyde. Two of these, the ' iodimetric ' and the 

 ' hydrogen peroxide ' being oxidation methods, 

 while the other two, the ' potassium cyanide ' 

 and Leglers's ' aimnonia ' methods, are based 

 upon condensation reactions. The oxidation 

 methods were found in all cases to give notice- 

 ably higher results than the condensation 

 methods. Test analyses made with the addi- 

 tion of alcohol, aldehydes and acetone indi- 

 cated that the difference was not due to the 

 influence of other substances present in the 

 formaldehyde solution, but to the reactions on 

 which the methods are based. Paraformalde- 

 hyde may be determined as readily as for- 

 maldehyde, with any of the four methods men- 

 tioned- The formation and properties of the 

 hexamethylene-tetramine, on which the am- 

 monia method depends, will be studied further. 

 H. 0. Sherman, 

 Secretary. 



DISCUSSION AND CORRESPONDENCE. 



ASTMMETEON LUCAYANUM IN BERMUDA. . 



Besides establishing the fact that Am- 

 phioxit^ cariioeus — knovpn since 1876 to exist 

 at the Flatts — is found in numerous localities 

 in these islands, the work of the station 

 this year has resulted in the discovery that 

 another representative of this very interesting 

 group of Chordates — Asymmetron lucayanum 

 — is also found in these waters. Especial 

 credit for the discovery of this more rare ani- 



mal is diie to Mr. Louis L. Mowbray, a young 

 Bermudian naturalist in the employ of the 

 station. E. L. Mark, 



Director. 

 Bebmuda Biological Station, 

 Flatts, Bermuda, July 22, 1904. 



THE ASCENT OF WATER IN TREES. 



To THE Editor of Science : It would not be 

 necessary to notice at all the note on ' The 

 Ascent of Water in Trees,' published in your 

 issue for July 22, were plant physiologists and 

 physicists alone to be considered. A single 

 remark, for the benefit of those who might be 

 misled, will suffice to show the futility of the 

 theory proposed. The structures at the lower 

 end of the conducting tissues are essentially 

 identical with those at the upper end. If at 

 the upper end the ' water ducts are protected 

 from direct atmospheric pressure by their 

 structures,' they are equally shielded from it 

 below. C. E. Barnes. 



The Univeesitt of Chicago. 



concerning spectacles. 

 Eather an extensive literature exists on the 

 question raised by Dr. 0. Barck in his paper 

 on ' The History of Spectacles ' (Science, 

 XX., July 8, 1904, p. 50) as to whether Nero 

 was near-sighted and viewed gladiatorial com- 

 bats with glasses. The passages in Pliny's 

 ' Natural History ' which have furnished food 

 for this discussion occur in xi. 54, and xxxvii. 

 16 ; and the best interpretation thereof known 

 to the writer of the present paragraph is found 

 in Dr. August Nies's interesting thesis ' Zur 

 Mineralogie des Plinius,' pp. 18-20 (Mayence, 

 1884). The claims of other alleged inventors 

 of spectacles besides those mentioned by Dr. 

 Barck are considered more or less fully in 

 Beckmann's ' History of Inventions,' and in 

 J. Fiedler's ' Geschichte der Erfindung der 

 Fernrohre.' C. E. E. 



SPECIAL ARTICLES. 

 the formation of toxic products by vege- 

 table ENZYMES. 

 No subject in the domain of plant chem- 

 istry has aroused more discussion of late than 

 the physiological role of the various enzymes. 



