August i6, 1900] 



NATURE 



375 



Stanley Flower, has become a popular place of resort for the 

 European visitors to Egypt, as well as for the Cairenes. The 

 receipts in 1899 were 3033/., of which 968/. were for gate- 

 entrances, and the expenditure was 3019/, The list of donors 

 includes many well-known names, amongst which we see those 

 of Sir William Garstin, Prince Omar Tousson, Sir F. Wingate 

 and Lord Kitchener. The Government of India presented an 

 elephant. Various new buildings were erected, and others were 

 reconstructed in 1899. The number of animals in the collection 

 on October i of that year was 473, against 270 at the corre- 

 sponding date in 1898. A list of wild birds that inhabit the 

 Ghizeh Gardens, and in many cases breed there, enumerates 

 nineteen species, amongst which is the European song-thrush 

 {Titrdus tnusicits). Two proboscis monkeys (A^asa/is larvatus), 

 presented by the Government of the Netherlands East Indies, 

 unfortunately did not live long. We are informed that since the 

 report was issued Captain Flower has succeeded in bringing to 

 the Ghizeh Gardens from the Sudan a fine young giraffe, 

 presented by the Sirdar. 



Writing from Mashonaland in May, Mr. G. A. K. Marshall 

 raises, in the August number of the Entomologist, what appears 

 to be a pertinent question with regard to mosquitoes and malaria. 

 If it be admitted, he observes, that malaria can only be carried 

 by mosquitoes of the genus Anopheles, and that these insects 

 can only acquire the microbes from malarially-infected man, 

 "then we are logically bound to accept the conclusion that if 

 a man, or party of men, free from malarial poison, should 

 penetrate from a healthy area into an unhealthy but uninhabited 

 region, it would be impossible for them to contract fever, how- 

 ever much they might be bitten by mosquitoes. Further, it 

 follows that all uninhabited regions, even of comparatively 

 small size (seeing that the range of individual species of Ano- 

 pheles is apparently very limited in extent) must be entirely 

 devoid of malaria, even though they may be full of swamps and 

 teem with mosquitoes." Such conclusions are, however, 

 contrary to experience, and if the writer's premises be correct, 

 his difficulty requires an explanation at the hands of specialists. 



The Walcott collection of Hymenoptera, now in the Cam- 

 bridge University Museum, his yielded to the researches of Mr. 

 R. C. L. Perkins ^^Entomologists' Monthly Magazine for 

 August) a species (OJyneriis tomentostts) new to the British 

 fauna. Considering that the greater part of the collection was 

 made in the first half of the century, it is not a little remarkable 

 that the species should have escaped notice so long. 



The large scale on which they do things in America has 

 Ijecome a proverb. An instance is afiforded by Mr. J. B. 

 Smith's description of one hundred new species of moths of the 

 family Noctuidne in vol. xxii. of the Proceedings of the U.S. 

 Museum. 



To vol. xxix. No. 13 of the Proceedings of the Boston 

 Society of Natural History Dr. H. S. Pratt contributes an im- 

 portant paper on the embryological history of the so-called 

 imaginal discs of the sheep-tick {Melophagus avintts). For the 

 benefit of our non-entomological readers it may be mentioned 

 that these imaginal discs, or folds, are structures in the larva 

 and pupa which do not participate in the general breakdown 

 of tissue at the periodical changes, but undergo continuous 

 development into the corresponding parts of the perfect insect. 

 Hitherto, the author says, these structures have been studied 

 only in the larval and pupal stages ; and he for the first time 

 describes their origin and early stages of growth. 



Four out of the nine papers in Part i. of the Proceedings of 

 the Philadelphia Academy for 1900 are devoted to the land and 

 fresh-water molluscs of America. In the first of these Mr. 

 NO. 1607, VOL. 62] 



C. T. Simpson descri!)es a numl)er of new or unfigured river 

 mussels (Unionidas) ; the second, by Mr. W. H. Dall, treats of 

 the land-shells of some of the Pacific Islands, more especially 

 those of the Galapagos and Cocos groups ; in the third, Mr, H. A. 

 Pilsbry discusses the anatomy of the helicoid genus Ashmun- 

 ella, and in the fourth the molluscs of the Great Smoky Moun- 

 tains. This last communication is perhaps the one of most 

 general interest, since the author is of opinion that the cleft in 

 the Appalachian chain formed by the valley of eastern Tennessee 

 indicates the boundary between two zoogeographic provinces. 

 The lists of terrestrial molluscs given by him as respectively 

 characteristic of the eastern and western divisions of this portion 

 of the chain seem to bear out his contention as to the existence 

 of two distinct faunas. 



The sixth of the series of physico-mathematical handbooks 

 published by Messrs. Carre and Naud, of Paris, under the title 

 of " Scientia," is a small treatise by M. Fred. Wallerent on 

 crystalline groups and their optical properties. As an introduc- 

 tion to modern crystallography the little volume should be of 

 much use to those interested in other branches of science who 

 are desirous of acquiring a general knowledge of the history and 

 fundamental principles of the subject, and who do not possess 

 the spare time for mastering a larger treatise. 



In a short note contributed to the Atti del R. Istituto 

 cT Incoraggiamento (Naples), Prof. E. Semmola discusses the 

 state of our knowledge of the variations of the electrical poten- 

 tial of the air with the altitude. In reference to Le Cadet's 

 result that the potential decreases with the altitude, Prof. 

 Semmola points out that the late Prof. L. Palmieri, in conjunc- 

 tion with himself, had established a similar property previously. 

 Le Cadet found that the potential decreased from 150 to 44 volts 

 in the first kilometre of altitude, and deduced that the potential 

 decreased much less rapidly at greater altitudes. But Semmola 

 thinks that the high potential found at the surface of the earth 

 was at any rate in part due to the obscurity of the superincumbent 

 air. 



A SHORT note on the reflection of light in the neighbourhood 

 of the critical angle is given by Mr. J. G. Coffin in the Techno- 

 logy Quarterly, the object being to examine more fully than 

 is done in most text-books the consequences of applying 

 Fresnel's formulae to refraction from a denser to a rarer 

 medium. Tables are calculated by the author and Prof. Picker- 

 ing, showing the percentages of light reflected at diflferent in- 

 cidences in passing from a rare to a dense medium and vice 

 versd, and the results are exhibited graphically by curves. The 

 paper thus contains an amplification of the superficial information 

 contained in the majority of treatises on optics. 



In ^}\t Journal of Proceedings of the Institution of Electrical 

 Engineers, xxix. 142, 1900, Mr. Alexander Russell discusses the 

 question how condenser and choking-coil currents vary with the 

 shape of the wave of the applied electromotive force. Various 

 forms of wave being considered, the author finds that the sine 

 curve wave produces the least effective current when applied to 

 a condenser, and the largest magnetising current when applied 

 to a choking-coil. Similar results are established for the sym- 

 metric wave in the case of a family of waves of equal height. 

 The subject is sufficiently interesting to make us wish for a fuller 

 mathematical investigation, Mr. Russell's note being a mere 

 statement of results. 



Some tests of fire retardent materials are described by Mr. 

 Charles L. Norton in the Technology Quarterly, xiii. 2, for June 

 1900. The tests were made on October 5, 1899, and February 

 3, 1900, by setting up small buildings previously constructed 

 in the Massachusetts Institute of Technology and building a 

 fire of wood and oil inside. Observations of the progress 



