May iS 



3.] 



SCIENTIFIC NEV\AS. 



471 



incandescent gas-burner, by Messrs. Johnson, Matthey 

 and Co. ; photographs of flashes of hghtning, by 

 the Royal Meteorological Society ; model of a maxi- 

 mum pressure anemometer, by Mr. Whipple ; charts, 

 showing lines of equal values of the magnetic elements 

 over the globe in 1880, by Staff-Commander Creak; 

 an ants' nest, from Sierra Leone, and also a series 

 of living pictures in insect life, shown on a glass 

 screen, by the aid of a lantern, by Mr. H. Burns ; 

 and a system of ballot for members of Parliament, 

 etc., uniting perfect secrecj' with a minimum ot cost, 

 by Mr. J. Leighton. 



At intervals during the evening Dr. Marcet, by means 

 of a camera lens, threw on a screen magnified images of 

 electric sparks from a large electrical influence machine, 

 in order to illustrate flashes of lightning. By means of 

 the new electric lantern Prof. Kennedy exhibited some 

 views illustrating the progress made with the erection of 

 the great steel cantilevers spanning the 1,700 feet wide 

 openings of the Forth Bridge. Mr. A. Sopwith exhibited 

 a number of interesting views, showing the interior 

 workings of a colliery ; and Dr. Hickson showed some 

 slides by Mr. Poulton of the true teeth of the Ornitho- 

 rhynchus paradoxus. 



THE SENSE OF SMELL. 



SOME remarkable facts have lately been brought 

 forward about the sense of smell. The delicacy of 

 this sense has been carefully tested by a series of very 

 interesting experiments. The whole matter is being 

 investigated on a most extensive scale ; but the facts 

 already substantiated are certainly striking. 



A series of solutions of each of the following substances 

 was prepared : oil of cloves, nitrate of amyl, extract of 

 garlic, bromine, and cyanide of potassium. Each series 

 was so arranged that every solution was of half the 

 strength of the preceeding one. These series were 

 extended by successive dilutions, till it was impossible to 

 detect the odours. The order of the bottles containing 

 these solutions was completely disarranged, and the test 

 consisted in the attempt to properly classify them by the 

 sense of smell alone. Seventeen male observers and 

 seventeen female observers were selected from the 

 principal apothecaries' shops, and each was required to 

 arrange the bottles. The average of the males detected 

 the smell in the solution of oil of cloves with i part in 

 88,000 of water, whereas the average of the females 

 could only detect smell in the solution with i part in 

 50,000 of water. Nitrate of amyl was detected by the 

 males with i in 783,000, and by the females with r 

 in 311,000; extract of garlic by males i in 57,000, by 

 females i in 43,000 ; bromine by males i in 49,000, 

 by females i in 16,000 ; and cyanide of potassium by 

 males i in 109,000, by females i in 9,000. 



A fresh series of experiments of a similar nature was 

 made with other observers on other substances, in order 

 to verify the results. Twenty-seven males were selected 

 and twenty-one females, the substances being prussic 

 acid, oil of lemon, and oil of wintergreen. The solutions 

 were prepared, the bottles disarranged as before, and 

 the observers successively set to the work of classification. 

 The average of the males detected the odour of the 

 prussic acid in a solution of i part with 1 1 2,000 of water, 

 whereas the average of the females could only detect the 

 smell in the solution of i part with 18,000 of water. Oil 



of lemon was detected by the males with i in 280,000, 

 by the females with i in 116,000; and the oil of winter- 

 green by the males with i in 600,000, and by the 

 females with i in 311,000. Again there was a very 

 great preponderance in favour of the males as to the 

 sensitiveness and discrimination of the sense of 

 smell. 



So acute was the sense of smell in two of the male 

 observers that they were able to detect one part of 

 prussic acid in about two million parts of water, and it 

 has no very decided smell, only a strange fustiness. 

 Careful chemical tests failed to show the presence of 

 prussic acid in several of the more dilute solutions in 

 which it was detected by the sense of smell. We 

 remember an experienced druggist who could tell what 

 was in a physic bottle better by the sense of smell than 

 by any other means ; but we were never aware, until 

 these experiments were made, that the sense was so 

 acute and discriminating. Two unexpected facts have 

 been established — that males (on an average) are far 

 more sensitive as to smells than are females, and that 

 in some persons it is more discriminating than the 

 subtlest chemical tests. 



But a very remarkable case has lately come before us. 

 Dr. Fischer used mercaptan and chlorophenol as the 

 odoriferous substances, and experimented in a room of 

 9,000 cubic feet capacity. He dissolved 70 grains of 

 each substance in a separate gallon of water. Of the 

 solutibn of one he took some drops and put them into a 

 quantity of pure water. With a fine jet he directed this 

 solution in a spray to all parts of the room, the air of 

 which was subsequently agitated by the waving of a 

 flag. Experimenters came in by turns and detected the 

 scent. The result arrived at is marvellous. Experts 

 were able to detect the three hundred millionth part of a 

 grain of chlorophenol, and even a thousandth part of 

 that quantity of mercaptan was distinctly recognised. 



«-^*^x^5eP-* — - 



EXPERIMENT ON SONOROUS CON- 

 DUCTIVITY. 



A NUMBER of rods of the size of a common lead pencil 

 areprepared from rubber, cork, gutta percha, wood,^ 

 glass, and steel, and, in order to facilitate the experi- 

 ment, are united in threes by means of rubber bands, 

 fragments of tubing of the same substance being inter- 

 posed between them. To perform the experiment,, 

 place one end of the rods on a resonant box, and, hold- 

 ing them with one hand, touch their free ends in 

 succession with the handle of a vibrating tuning fork. 

 The sound is not audible when the rubber rod is touched, 

 and becomes louder and louder when the entire series of 

 rods is passed successively in review. By this method, 

 the laws of sonorous conductivity are easily demon- 

 strated, and it is shown that the intensity of sound 

 remains constant, if we substitute one rod for another 

 of the same substance, but of which the length and 

 section vary in the same ratio. On varying the length 

 only, we change the intensity, as we do also when we 

 vary the section and leave the length constant. This 

 method may be employed also for demonstrating the 

 difference in conductivity of wood parallel with and 

 perpendicular of the fibres, and even for determining the 

 numeric ratio otthese two conductivities. — lour. Russian 

 Physico-Chem. Soc. 



