October 13, 1904] 



NA TURE 



58: 



should be prepared by persons who have lived in them and 

 have made special studies of the varied conditions of 

 climate. Undoubtedly no meteorologist living could be 

 found who is better qualified than Dr. Hann, whose 

 laborious works are well known to our readers, to prepare 

 a pattern for the guidance of the persons undertaking the 

 subsequent parts. His memoir embraces 104 pages, con- 

 taining fifty years' monthly and yearly means of different 

 localities, a general summary, and special discussions of 

 the more important phenomena. The work is in every 

 respect worthy of the very high reputation of its author. 



An interesting note on the form of Britain, as described 

 by Tacitus, is contributed to the Lombardy Rcndiconti 

 (xx.wii., 16) by Prof. Giovanni Ferrara, who considers 

 that, of all the Romans, Tacitus had the clearest ideas as 

 to the configuration of our island, and that Ptolemy's map 

 was to a large extent founded on his descriptions. 



Prof. Luigi Gabba, writing in the Lombardy Rendi- 

 coitti, (2) xxxvii., 16, discusses the problem of teaching 

 chemistry for technical purposes in Italy, and strongly sup- 

 ports the recent resolutions proposed at the Turin Congress 

 of 1902 by Prof. Cannizzaro urging the Government to 

 provide instruction in technical chemistry, in addition to the 

 existing university instruction of a more theoretical 

 character. 



The learning of modern languages is of such importance 

 to science workers that interest attaches to Prof. Charles C. 

 Ayer's paper on the subject in the University of Colorado 

 Studies. The author considers that the ability to speak 

 a foreign language fluently depends very largely on a kind 

 of dramatic instinct or power of imitation which seems to 

 project the speaker into a new and foreign personality, and 

 he instances the case of .Americans who return from a com- 

 paratively short residence in England. letter perfect in the 

 Rnglish pronunciation, vocabulary, phrasal intonation, and 

 English manner generally. 



What is the "Codex Atlanticus ''? is a question which 

 Signer Luca Beltrami answers in a paper reprinted from 

 l.ettura, and published at the offices of the Corriere delta 

 Sera at Milan. The name has been given to one of the 

 most interesting works of Leonardo da Vinci, on account 

 of its resemblance in form to an atlas. In 1637 it was 

 given to the Ambrosian Library at Milan, and a reprint has 

 now been produced under the auspices of the Reale Acca- 

 demia dei Lincei, of which Messrs. Hoepli, of Milan, have a 

 few copies still in their hands. The thirty-five parts occupy 

 more than 1300 pages, and contain 1384 heliotype illus- 

 trations, many of them in colours. The edition was limited 

 to 280 copies, the first of which was presented to President 

 Loubet on his visit to Milan. The work of transcription 

 was undertaken by Dr. Giovanni Piumati, and an interest- 

 ing feature of the first part is the preface, written by the 

 late Prof. Francesco Brioschi, describing the history of the 

 " Codex " from the death of Leonardo da Vinci to the 

 present date. 



M. Charles FIiRV describes in the September part of the 

 Journal de Physique a convenient form of telescope pyro- 

 meter for measuring temperatures between 500° and 1200°. 

 The heat rays are concentrated by a silvered concave mirror 

 upiin a thermo-couple placed at its focus; the reading of a 

 galvanometer connected with the thermo-couple gives the 

 temperature, and the instrument is so designed that the 

 indications are independent of the dimensions of the source 

 of heat and its distancp. 



NO. 1824. Vdl,. 70] 



The .August number of the Physical Rei-iew contains an 

 interesting note by Mr. W. Coblentz on the infra-red 

 absorption spectrum of selenium. Whereas commercial 

 selenium, which contains sulphur, gives immediately after 

 fusion and re-solidification an absorption which rapidly and 

 regularly increases from i/x to 14/*, after two days it shows 

 nearly a constant transmission throughout the whole of the 

 same range. This peculiar change in transparency is not 

 observed with pure selenium, as the same transmission 

 curves are obtained immediately after solidification and 

 after an interval of thirty days. It is a striking fact that 

 the transmission curves of sulphur are totally different in 

 character from those of selenium. 



A PAPER by Mr. F. E. Hackett on the photometry of the 

 It-rays, which is published as part x. of vol. viii. of the 

 Transactions of the Royal Dublin Society, appears at a 

 very opportune moment. In view of the failure of Profs. 

 Rubens and Lummer to reproduce M. Blondlot's results, 

 and Prof. R. W. Wood's strictures on the methods hitherto 

 employed in their investigation, a method for their quanti- 

 tative measurement becomes particularly worthy of notice. 

 Mr. Hackett has studied the variation of sensitiveness over 

 the retina when habituated to darkness, and claims to have 

 eliminated in this way all subjective variation. The method 

 of measurement adopted shows that whilst the ii-rays 

 emitted by unannealed glass cause an increase of approxi- 

 mately 10 per cent, in the brightness of a phosphorescent 

 screen, the increase produced by a silent tuning fork is very 

 small, being about 3 per cent. The experiments described 

 are stated to be of such a nature that any person without 

 special training with a little patience may reproduce them. 



In the August number of the Physical Rei:iew Mr. K. E. 

 Guthe has made a comparative study of the various types 

 of silver voltameters which are used for measuring the 

 strength of electrical currents. From the measurements 

 which are recorded it appears that there are two distinct 

 classes of silver voltameters, one class including the ordinary 

 type and Leduc's modification, the other Richard's and the 

 ■' large anode " types. The voltameters of the second class 

 give a deposit weighing about 005 per cent, less than that 

 given by the first class. It appears that in those types of 

 voltameters in which the anode is enveloped merely by filter 

 paper or muslin, the heavy liquid surrounding the anode 

 penetrates through and reaches the kathode, depositing there 

 a complex silver ion. As a consequence, the observed in- 

 crease in weight is greater than that corresponding with the 

 true electrochemical equivalent of silver. In Richard's volt- 

 ameter and the " large anode " modification, the deposition 

 of a complex ion is prevented by surrounding the anode 

 with a porous pot so as to exclude contact between the 

 anode-liquid and the kathode. As in this case the variation 

 in the amount deposited by the same current in various 

 experiments does not exceed i in 10,000, it is recoinmended 

 that, in future, the " legal " form of silver voltameter 

 should be superseded by the improved form. .A re-determin- 

 ation of the electrochemical equivalent of silver gave a 

 mean value of i]i6S3 mg. per coulomb. 



The publication committee of the Chemical Society has 

 adopted the word " radicle " in the place of " radical " in 

 their publications. The alteration does not meet with the 

 approval of a hundred and seventy-nine fellows of the 

 Society, who have addressed a letter to the president of the 

 society asking him to bring the matter before the publi- 

 cation committee with a view to its alteration. The 

 signatories point out that ;— (i) The new word "radicle" 

 does not convey the sense which the authors of the word 



