August 15, 1901] 



NA TURE 



also like to see dietary studies taken in periods of exceptional 

 brain activity, as, for example, on subjects sitting for a com- 

 petitive examination. 



An interesting and useful pamphlet has recently been issued 

 by Mr. A. Hilger, containing full description and details of 

 manipulation of the Michelson Echelon Grating. Many of the 

 principal Universities of Europe have been provided with this 

 very powerful means of spectroscopic determination, and the 

 experience gained has been sufficient to permit the designing of 

 a standard type of instrument. In this the thickness of each 

 plate is 10 mm., and the width of each step I mm. The pro- 

 gressive precision in the working of the plates has enabled Mr. 

 Hilger to avoid the considerable loss of light which was caused, 

 in the original instruments, by the plates not being mechanically 

 clamped together. They are now held in position by a screwed 

 frame, which can be so adjusted that no distortion is per- 

 ceptible, while the increase in brilliancy of the spectra is very 

 noticeable. 



Wireless telegraphy is in use upon ships engaged in the 

 naval manoeuvres, and it enables a battleship to communicate 

 with a cruiser fifty or sixty miles away with greater ease than the 

 same ship could be communicated with at a distance of ten 

 miles in clear weather a year or two ago. But the Times 

 special correspondent with one of the fleets remarks that the 

 method, although independent of the weather, is still subject to 

 one very serious drawback. The communication is not, and 

 cannot be, a private or exclusive one, except so far as the mes- 

 sages are transmitted in cipher. Even so, every ship within 

 range which is fitted with the necessary apparatus can take in 

 the message, and if an enemy's ship is within range she can, by 

 setting her own apparatus at work, break up the message and 

 render it unintelligible. It is perhaps more politic to take it 

 in clandestinely and work out the cipher — a thing which it is 

 seldom very difficult to do and never altogether impossible if 

 sufficient cipher material be obtained and sufficient time be 

 devoted to the task. The moral is to employ as difficult a cipher 

 as possible and to change it as soon as there is any reason to 

 suspect the enemy has discovered it. But, even so, wireless 

 telegraphy as at present practised is full of limitations and pit- 

 falls which only experience caneliminate. It will never be quite 

 satisfactory for war purposes until the transmitting instrument 

 can be so adjusted as to emit vibrations of different pitch at 

 the will of the operator and the receiving instrument rendered 

 sensitive only to vibrations of a given pitch at a given moment. 

 In that case, every ship in a fleet could have its own pitch and be 

 sensitive only to messages addressed to itself in that particular 

 pitch, while, unless an enemy within range happened to be 

 attuned to the same pitch at the moment — a very unlikely con- 

 tingency if the pitch were changeable at will — he would be 

 powerless to intercept the message. 



The electrolytic dissociation theory of Arrhenius is severely 

 criticised by Prof Kahlenberg in a paper in the Bulletin of the 

 University of Wisconsin (No. 47, February 1901), in which a 

 great deal of experimental evidence in contradiction to the 

 theory is brought forward. Prof Kahlenberg has measured 

 the conductivity of a number of electrolytes at o' and 95° and 

 calculated the degree of dissociation from these measurements 

 as well as from determinations of the lowering of the freezing 

 point and rise of the boiling point. The two sets of results he 

 has thus obtained are far from concordant, from which he con- 

 cludes that the dissociation theory is incorrect and doomed to 

 early extinction. This theory, even though it has not met with 

 universal acceptance, is not, we think, to be so easily over- 

 thrown, especially until some more satisfactory and fruitful 

 alternative hypothesis is put forward to take its place. It is 

 NO. 1659, VOL. 64] 



interesting to note that another American professor, Prof. H. C. 

 Jones, of the Johns Hopkins University, is now contributing a 

 series of valuable "Chapters in Electrochemistry" to the 

 Electrical Review of New York, in which the subject is treated 

 entirely from the point of view of the ionic theory, of which 

 Prof. Jones is a vigorous adherent. 



The Times correspondent at Simla states that since the 

 Pasteur Institute at Kasauli was opened a year ago, 321 patients 

 have been treated, including 96 from the British Army and 50 

 European civilians. Not a single failure has occurred among 

 the Europeans, but two natives died. Both of the latter had 

 been badly bitten and arrived too late to be saved. The complete 

 success of the Institute, which is under the charge of Major 

 Semple, of the Army Medical Service, means a great saving to 

 the Government, as soldiers need no longer be sent to Paris for 

 treatment. It is hoped that funds will be provided to make 

 possible the preparation of anti-toxins for enteric, snakebite and 

 tetanus. 



It is a matter for regret when familiar names like Octopus 

 have to disappear from the effective list, yet, according to Mr. 

 Hoyle (Manchester Memoirs, xlv. No. 9), this must be replaced 

 by Polypus on the ground of priority. In the same communica- 

 tion, the question is raised whether the name Histiopsis is pre- 

 occupied by Histiops — a point on which experts differ. In 

 No. 4 of the same serial, Mr. Hoyle gives an instance of the 

 danger of making genera and species on imperfect specimens. 

 Part of a cuttlefish taken from a sperm-whale's stomach was 

 referred to a new genus on account of its being apparently 

 covered with regularly arranged quadrangular scales. Specimens 

 recently acquired suggest that the appearance in question was 

 due to decomposition. 



The secretary of the British South Africa Company has sent 

 us a copy of the " Reports on the Administration of Rhodesia, 

 1S98-1900," issued by the Company. One section is devoted 

 to " Notes on the Fauna and Flora of North-eastern Rhodesia," 

 by Mr. C. P. Chesnaye. From this we learn that th6 prospect- 

 of the survival in considerable numbers of the larger mammals 

 and reptiles m the district to the west of Loangwa and in the 

 swamps of Bangweolo and Mweru is very hopeful. The elephant 

 is still met with in large herds, owing to its living for the greater 

 part of the year in almost inaccessible swamps. The formation 

 of a game-reserve to the east of Lake Mweru will probably 

 largely aid in the preservation of this and other species, as it is 

 believed that the elephants now hunted bySwahili traders to the 

 south of Tanganyika will gradually retire to the reserve. 

 Rhinoceroses are still fairly numerous, while hippopotamuses 

 abound. The rinderpest which swept over the country in 1893 

 decimated the buffalo, eland and lichi antelope, but the country 

 is gradually recovering from the scourge, and most districts are 

 now very rich in game of all kinds, especially roan antelope, 

 eland, Lichtenstein's hartebeest, puku, lichi and zebra. A few 

 of the beautiful sable antelope still survive in the Mweru district, 

 and around the north end of the lake the swamp-loving sitatunga 

 antejope is plentiful. The rare sassabi hartebeest is restricted to 

 a small area west of Lake Bangweolo. The dreaded tsetse-fly 

 is stated to be prevalent in the valley of the Loangwa from the 

 Zambesi to the confines of the Nyasa plateau, as well as in one 

 other district, but to be absent from the greater portion of the 

 Bangweolo country. Whether the latter part of the statement 

 is true requires confirmation, but most of the territory seems free 

 from " fly." 



We have received from the New Mexico College of Agri- 

 culture Bulletin No. 37, containing " Notes on the Food of 

 Birds," by Mr. T. D. A. Cockerell. This is chiefly of local 

 interest. 



