156 



HARDWICKE'S SCIENCE-GOSSIP. 



of noses," for the purpose of determining the existence 

 or non-existence of certain aromatic compounds, and 

 frequently pondered on the humiliation to chemical 

 analysis which sometimes followed, as when by the 

 simple dog-like use of olfactory organs greatly inferior 

 to those of a dog, we were able to detect the exis- 

 tence of substances which no chemical reagent could 

 reveal. 



This humiliation has recently been elaborately 

 displayed by some experiments of Drs. Emil Fischer 

 and Pensoldt. They used mercaptan and chlorophenol, 

 diffused them through a room of 230 cubic metres 

 capacity, in such wise that the quantities were 

 measurable by the degree of dilution and cliff usion. 

 The results obtained were that human olfactory organs 

 were able to detect 4bl ^ J0( ) part of a milligramme of 

 chlorophenol, and the ^j^noc part of a milligramme 

 of mercaptan (a milligramme is jgi^ part of an ounce). 

 Chemical testing was cruelly beaten by the spectro- 

 scope when applied by Bunsen and Kirchhoff for the 

 detection of sodium vapour in the air, but in these 

 experiments on mercaptan the unassisted nose detected 

 a quantity 250 times less than the smallest quantity 

 of sodium vapour detected optically by the spectro- 

 scope. 



Measuring Distance by Electric Light. — 

 The " Electrician " tells us that M. E. Genglaire has 

 devised a simple and ingenious method for enabling 

 an ironclad to determine the range of an object after 

 nightfall. He proposes to mount two powerful 

 electric light projectors, one at the bow, the other 

 at the stern of the vessel, and converge their beams on 

 the object in question. By taking the distance 

 between the two lights as a base line, and measuring 

 the angles of projection at each end of the line, the 

 distance of the object upon which the two lights 

 converge may be easily calculated. 



The w r riter of the paragraph adds that "it is 

 obvious that the method does not pretend to any 

 great accuracy, but it seems to be capable of 

 sufficiently close approximation for the purpose in 

 view, to make it worth while for the Admiralty to 

 try some experiments in this direction." 



In this criticism the writer is seriously at fault. 

 Such a method properly conducted admits of remark- 

 able accuracy, as anybody acquainted with the use of 

 the theodolite in trigonometrical surveys will at once 

 understand. Unless the ship be rolling, a distance 

 across the water may thus be measured more ac- 

 curately than across ordinary and undulating ground 

 by direct application of the chain or measuring tape. 

 On this principle were measured the distances between 

 different parts of Great Britain as laid down on our 

 Ordnance maps ; the difference in the application 

 of the principle being that in the case of the Ordnance 

 and other good surveys, rays of light passing from the 

 distant object to the ends of the base line are used ; 

 while in this light projection method, the rays proceed 



from the ends of the base line to the object. The 

 primary base line of the Ordnance survey was measured 

 on the sands of Lough Foyle instead of a ship's deck. 

 A theodolite arrangement may easily be applied to 

 the light projector by making it take the place of a 

 theodolite telescope. 



THE CORAL-ROOTS OF SWITZERLAND. 



BEFORE the February frosts give way to the 

 early Swiss spring, there are many indications 

 of the forthcoming mountain flora. Here, in the 

 Canton Vaud, we may follow the wild course of the 

 ravine and torrent bed, which gradually narrows 

 between the precipitous crags and spurs of the green 



Fig. 80. — Dcntaria pinnata, half natural size. 



Alps as we approach the higher fastnesses. Massive 

 limestone, lichen-covered boulders impede the 

 foaming stream, and tangled masses of the previous 

 year's vegetation clothe the rocky sides. At times 

 the very streams are frozen ; huge icicles hang on 

 every side, and botryoidal-shaped ice encasing the 

 very stones, while the far-off trickle proclaims the 

 fact that the waterfalls and streams are still active 

 behind the veil of glittering ice. There is a peculiar 

 charm in the valley at such a time, for no breath of 

 wind can reach us ; the sky is intensely blue, and the 

 power of the sun is great. Everything glitters and 

 sparkles in the brilliant light, until we imagine our- 

 selves in fairy-land. And, in truth, it is like some 

 enchanted ground. That spring is at hand is evident, 

 the early snow-flake (Leucojum venium, L.) has 

 already pierced the snowy slopes in profusion, and 



