January 13, 1898] 



NATURE 



255 



told in the January number of Pearson's Magazine. A little 

 consideration will show that the tunnel offers ideal conditions for 

 the growth of mushrooms ; the temperature varying but very 

 slightly, and light being absent. The result of this combina- 

 tion of favourable conditions is that the Scottish Mushroom 

 Company now practically control the market in cultivated mush- 

 rooms. The Company has eight hundred mushroom beds in the 

 tunnel, each about 12 feet by 3 feet in size. When in full 

 operation about one thousand bushels of spawn are used yearly. 

 The highest output reaches five thousand pounds of mushrooms 

 . per month. The steady and constant supply has killed foreign 

 competition in mushrooms ; for it appears that, whereas ten years 

 ago the quantity of French mushrooms consumed in Great 

 Britain largely exceeded those of home growth, they form at 

 present only about one-hundredlh part of the total supply. 



A NUMBER of remarkable instances of hallucinations con- 

 nected with hemianopia, or complete blindness in one or other 

 half of the visual field, are described by Dr. W. Harris in the 

 course of an article in the new number of Brain. In one case 

 of partial hemianopia the patient had visual hallucinations, 

 lasting a few minutes, of folk and horses moving in a reddish 

 atmosphere, the visions being limited to the blind field of 

 vision. Another saw continually in his blind field a man stand- 

 ing at the back of his head, holding two lighted candles. A 

 man who developed right hemianopia was troubled ten days 

 later with hallucinations of men, flies, insects, &c. At first he 

 recognised their unreality, but after a few days he became con- 

 vinced they were real. The spectres became more frequent, 

 and he would then hunt for t' em in cupboards and corners. 

 Another case of hemianopia with hallucinations in the blind 

 field, is that of a man who suddenly lost power of speech, using 

 wrong words, and forgetting the names of things. During a 

 subsequent attack of temporary loss of speech he suddenly 

 noticed while reading that his sight was confused, and that the 

 print seemed to run together. After that he noticed he could 

 not see so well to the right, and he used to bump up against 

 things on his right side, and had to be careful whilst crossing 

 the road. He also has had visual hallucinations of animals and 

 faces moving about to his right. Dr. Harris discusses the seat 

 of production of visual hallucinations of this kind, and concludes 

 that they cannot be elaborated in the half-vision centre in the 

 cuneus of the brain, but in a higher visual centre — possibly the 

 angular g>'rus. 



Prof. Plateau's experiments on the conditions which 

 induce insects to visit flowers have been referred to on several 

 occasions (see p. 179). It is worth while, however, bringing 

 the facts together. In the concluding part of his series of 

 papers, " Comment les fleurs attirent les insectes," in the Bnll. 

 de r Acad, des Sciences de Belgiqiie, Prof. Plateau thus sums 

 up the results at which he has arrived. In seeking for pollen 

 or nectar, insects are guided only to a subsidiary extent by the 

 sense of sight. They continue to visit scented flowers after 

 the coloured parts have been almost entirely removed. When 

 flowers of the same species vary in colour, they exhibit neither 

 preference nor antipathy for one colour over another. Incon- 

 spicuous flowers hidden among foliage attract large numbers 

 of insects. Artificial flowers made of paper or calico, even 

 when brightly coloured and closely resembling real flowers, are 

 not visited by insects ; but they are when made of green leaves 

 which have a vegetable scent. If flowers which have little or 

 no nectar, and which are therefore habitually neglected by 

 insects, are smeared with honey, insects are attracted in large 

 numbers. On the other hand, if the nectary is removed from 

 flowers habitually visited, their visits cease at once. The author 

 has paid especial attention to entomophilous flowers, and finds 

 that their exemption from the visits of insects is due mainly to 

 NO. 1472, VOL. 57] 



their not providing them with honey. From all these facts M. 

 Plateau draws the conclusion that the guiding sense to insects 

 in visiting flowers must be chiefly the sense of smell. 



Writing in \\i& Revue generate des Sciences for December 30, 

 1897, Dr. Louis Olivier describes the latest combination of the 

 principles of the microphone and phonograph under the name 

 of microphonograph, the invention of M. F. Dussaud, of 

 Geneva, and which has been subsequently developed by M. 

 George F. Jaubert and M. Berthon. A demonstration of the 

 properties of this apparatus was given a short time ago at the 

 house of M. and Mme. Eugene Pereire. From certain physio- 

 logical facts, Dr. Laborde showed the possibility of rendering 

 sounds audible to deaf mutes by this instrument, and his view 

 received practical confirmation at the hands of Dr. Gelle, who 

 experimented with signal success on a number of subjects to 

 whom a sensation of sound was thus conveyed for the first 

 time. It is suggested that the micro-phonograph may become 

 an important factor in the education of deaf and dumb sub- 

 jects. It will be remembered that a method of giving deaf 

 mutes the feeling, or at all events the rhythm of music, was 

 devised by Prof. McKendrick, and has been described in 

 these columns (vol. Ivi. p. 212). Finally, M. Berthon and M. 

 Jaubert have employed the new apparatus in connection with 

 the telephone and the kinematograph, the latter combination 

 rendering it possible to reproduce scenes with all the attendant 

 sounds of conversation and so forth. With this apparatus it is 

 proposed to arrange life-like reproductions of a number of naval 

 scenes at the Exhibition of 1900, under the auspices of the 

 Compagnie generale Transatlantique. 



Where certain salts, such as bromide of potassium and 

 chloride of sodium, undergo changes of colour under the action 

 of kathodic rays, after the method of Goldstein, it has been 

 found by Profs. Elster and Geitel that they are at the same 

 time rendered photo-electiically sensitive, inasmuch as in sun- 

 light or broad daylight they lose any negative electric charges 

 imparted to them more rapidly than in the dark. The same 

 physicists, writing in Wiedemann'' s Annalen (62), now examine 

 whether the same property is conferred on these salts when the 

 coloration is produced by heating them in the presence of 

 potassium or sodium vapour, after the manner described by 

 Kreutz and Giesel. In the case of common salt, the electro- 

 meter readings representing the loss of charge in one minute 

 in light were as follows : — For salt coloured by kathodic rays 

 and kept in darkness a year, 214 ; rock-salt coloured brown to 

 blue by potassium vapour, 73 ; natural violet salt, 23 ; chloride 

 of sodium coloured by Berlin blue, -1- i ; the corresponding 

 data in the dark being o, - 10, - 2, - 3. With potassium 

 bromide, nearly blackened by potassium vapour, in light, 171 ; 

 the same bright blue, lOi ; the same coloured by Berlin 

 blue, -f I ; the results in darkness being -4, -F 2, o-. There 

 is thus no doubt that the same photo-electric properties are con- 

 ferred on the salts by potassium vapour as by kathodic rays ; 

 and, moreover, these properties exist mere or less in the natural 

 violet and blue varieties of such minerals as rock-salt and 

 fluor-spar. 



A DETAILED account of experiments in gliding flight is 

 contributed by Mr. Octave Chanute to the lotirnal of the Western 

 Society of Engineers (U.S.A.) for 1897. After trying many 

 different types of gliding machines, some with as many as six 

 superposed pairs of wings, Mr. Chanute seems to have chosen 

 for 'his later experiments a form of apparatus with two narrow 

 superposed aero-curves of rectangular form. The most note- 

 worthy feature of Mr. Chanute's investigations is his invention 

 of a regulating mechanism by which the fore and aft equilibrium 

 and stability is automatically maintained without any exertion 

 or special agility on the part of the operator, and even the 



