February 19, 1903] 



NA TURE 



375 



now in the palseontological museum at Florence. This 

 skull was referred by Forsyth Major and Riitimeyer to 

 Castor fiber. It is much more closely related to the Euro- 

 pean than to the Canadian beaver, particularly in the 

 shape of the nasal parts, the zygomatic arches, the 

 breadth of the frontal and nasal regions, and the pari- 

 etal crests; it differs, however, from both forms in Ihe 

 palate, which is much broader behind than before, the 

 incisors, which are broader, and the molars, which decrease 

 rapidly in size from the first to the last', and on the surface 

 of which the folds of enamel are slightly sinuous. At the 

 ■same time* the fact that the nasal bones have retained the 

 same form and breadth during the geological intervals 

 whii h have elapsed from the time of the Maspino beaver 

 and the Pliocene specimen of Valdarno Superiore affords an 

 argument in favour of the specific separation of Castor fiber, 

 L., from C. canadensis, Kuhl. 



M. L. Houllevigue describes in the Journal de Physique 

 for January some interesting results obtained by depositing 

 thin films of metal on glass and other surfaces by kathodic 

 rays in a bell glass receiver. With deposits of palladium 

 the moisture of the breath was sufficient to break up the 

 film, and the same was to a less degree the case with 

 platinum. In the case of copper, crystals of oxide com- 

 menced to form at the edges, and soon extended inwards, 

 but the process was arrested before reaching the middle 

 part, which was the thinnest portion of the pellicule. An 

 attempt was made, extending over seven days, to obtain 

 a carbon film, but the only deposit obtained was probably 

 due to the copper of the support. The electric resistance of 

 a film of bismuth obtained by projection was found to be in- 

 sensible to a magnetic field. On the other hand, trans- 

 parent laminas of iron, placed normally to the field of a 

 Ruhmkorff coil, afforded a ready illustration of magneto- 

 optic rotation. In connection with this work, M. Ed. van 

 Aubel calls attention to the investigations of Wright, Kundt, 

 Patterson and J. J. Thomson. 



" Factorisation of large numbers " is the subject of a 

 paper read by Mr. F. J. Vaes, of Rotterdam, to the Amster- 

 dam Academy of Sciences last year. The method which 

 forms the starting-point of Mr. Vaes's paper consists in 

 the expression of the given number as the difference of two 

 squares. Taking, say, the number 513667, the next greater 

 square is 717 2 , and he writes 513667 = 717* — 422. Then he 

 increases the first and second terms of the difference in 

 succession by 2.717+ 1, 2.717+3 . . ., that is, 1435, 1437, 

 1439 . . . ; the results are thus 71S 2 — 1857, 719 2 — 3294 . . . 

 and when the second term is a perfect square, the factorisa- 

 tion will be completed. However, the work may be 

 shortened by observing that a perfect square cannot end in 

 2, 3, 7 or 8, and further, the author gives a table of all the 

 groups of four figures in which a square can end, by which 

 further abbreviation appears possible. It is obvious that 

 the process stops when the original number 211+ 1 is ex- 

 pressed in the form (n+1) 2 — n 2 , and if a square has not been 

 obtained previously, the number will be known to be prime. 



Referring to Dr. E. H. Barton's letter, published in our 

 last issue, describing a simple sensitive flame, Prof. W. F. 

 Barrett, F. R.S., directs attention to a lecture delivered by 

 him before the Royal Dublin Society on January 3, 1868, 

 in which he thinks he used such a flame to demonstrate the 

 reflection and lefraction of sound. 



The short nature-studies written by Prof. L. C. Miall, 

 F.R.S., and published under the title " The History of 

 Aquatic Insects " by Messrs. Macmillan and Co., Ltd., in 



NO. 1738, VOL. 67] 



1895, have been issued in a cheaper form at 3s. (>d, Advan- 

 tage has been taken of the reissue to make a few emenda- 

 tions and additions. In its new form the book will doubt- 

 less secure a wide popularity in the classes for nature-study 

 which are being instituted in many. parts of the country. 



Messrs. George Bell and Sons have published separ- 

 ately, at 2S. net, under the title " Webster's Pictorial 

 Dictionary,'* the three thousand or more illustrations in. 

 " Webster's International Dictionary of the English 

 Language." The pictures have been classified and arranged : 

 according to subjects. As was, perhaps, to have been ex- 

 pected, a very large proportion of the figures illustrate 

 scientific subjects, and , exceptional prominence seems to 

 have been given to botanical and zoological terms. 



A second edition of " An Elementary Course of Infini- 

 tesimal Calculus," by Prof. Horace Lamb, F.R.S., has 

 been issued by the Cambridge University Press. The book 

 was first published in 1897, and a review of it appeared in 

 Nature for July 28. 1898. In the new edition the book has 

 been carefully revised, and several errors have been cor- 

 rected, principally in the examples. A few paragraphs in 

 the latter portion of the book, relating to infinite series, 

 'have been amplified. 



The seventh volume of The South-eastern Naturalist, be- 

 ing the Transactions of the South-eastern Union of Scientific 

 Societies for 1902, has been received. Amongst other 

 interesting contents, the volume contains the presidential 

 address, by Dr. Jonathan Hutchinson, F.R.S., on leprosy 

 in the Middle Ages, and the following papers : — Miss A. L. 

 Smith, on mycorhiza, the root-fungus ; Mr. E. R. Harrison, 

 on eolithic flint implements ; Prof. G. S. Boulger, on the 

 preservation of our indigenous flora ; Mr. E. A. Martin, on 

 the protection of plants ; Mr. Sibert Saunders, on the marine 

 aquarium, without circulation or change of water ; and Mr. 

 W. Whitaker, F.R.S., on Kentish wells and deep borings 

 in the neighbourhood of Canterbury. The report of this 

 union of scientific societies, with which the publication 

 begins, is of a highly satisfactory character, and the record 

 of the work accomplished, or now being done, by members 

 of the affiliated societies shows a very creditable activity on 

 the part of the union. 



The International Oxy-Generator Syndicate, Ltd., has 

 submitted to us for examination a simple and convenient 

 form of apparatus for the manufacture of oxygen, known 

 as the " ' Ever Ready ' Portable Automatic Oxygen Gener- 

 ator." The apparatus consists of a steel tube used as a 

 retort, a spirit lamp for heating the retort, a purifying tank 

 for washing and cooling the gas, an automatic travelling 

 stage, a collapsible gas holder for storing the gas, and all 

 the necessary connections. The whole of the parts pack 

 easily into a case of moderate size, and there are no com- 

 plications to get out of order or to puzzle the novice. The 

 oxygen is obtained in the usual manner by heating a mixture 

 ol potassium chlorate and manganese dioxide. As a means 

 of avoiding the difficulties of procuring cylinders of com- 

 pressed oxygen in out-of-the-way places, this generator 

 should prove very useful. 



In the Proceedings of the American Academy of Arts and 

 Sciences, vol. xxxviii. No. 5, T. W. Richards has published a 

 simple method of gas-analysis which requires only the simplest 

 apparatus and yet is capable of yielding results accurate enough 

 for many ordinary purposes. The actual measurement consists 

 in a determination of the pressure, the volume of the gas being 

 kept constant. As an elementary exercise for students, the use 



