HA RD IVICKE'S SCIENCE- G OSSIP. 



59 



author of " Les Poissons Fossiles," and " Etudes sur 

 les Glaciers," I must "improve the occasion" by a 

 preachment of warning to my readers. Beware of 

 the first symptom of second childhood ; the first film 

 which old age spreads over the intellectual vision ; 

 that blind conservatism that repels progressive inno- 

 vation int he region of your own speciality. Louis 

 Agassiz, the great progressive naturalist of fifty years 

 ago, died in darkness, having during his latter years 

 stubbornly shut his eyes against the new light of 

 biological evolution. 



Solidifying Gravel-drift. — On sinking the 

 shafts for a coal-mine, many difficulties are encount- 

 ered. Outsiders commonly suppose that the hardness 

 of the rocks to be penetrated is one of the greatest. 

 This, however, is far from being the case. When 

 the sinkers are going through what they call the 

 "metal," i.e. the hardest rocks of the district, they 

 are paid at a higher rate per yard for their work, but 

 this does not practically increase the cost, as such 

 rock may remain bare, without the ordinary brick 

 lining. Softer shaly rock requires such lining, and 

 in some cases " tubbing " with iron. But the worst of 

 all is loose ground — gravelly deposits which run in 

 from the sides of the sinking, filling up the shaft as 

 the men sink it, and imperilling the whole super- 

 structure of internal brickwork, as the subterranean 

 tower formed by the ordinary lining must necessarily 

 rest on something below. When such running ground 

 is encountered, this internal tower has to be supported 

 by chains or scaffolding, or both, while the battle 

 with the loose ground is fought below at hourly risk 

 of life, until a solid substratum is reached upon which 

 a lower tower is built to reach up to the one that is 

 undermined and suspended. 



The same difficulty may be encountered in tunnel- 

 ling — has been lately in making a tunnel at Stockholm 

 which passes through a hill of light wet gravel. The 

 contractor, Captain Lindmark, has successfully over- 

 come the difficulty by a novel and ingenious device. 

 He employs refrigerating machinery similar to that 

 which is used in supplying us with New Zealand and 

 Australian mutton. With this he converts the wet 

 gravel into solid rock, cuts it accordingly, and while 

 it yet remains frozen builds up the excavated portion 

 with suitable supporting masonry. We are told that 

 " the results have been in every way satisfactory, and 

 already several large houses have been safely passed 

 under." This being the case, but a small step further 

 is necessary in order to apply the same principle in 

 sinking pit-shafts through similar ground. 



Seeing the Invisible. — This apparent paradox 

 has actually been achieved — is in fact now becoming 

 quite easy of achievement ; and the invisible objects 

 displayed to sight exist both in the heavens above, 

 and in the earth beneath. Our eyes can only show 

 .us the impressions that are made instantaneously on 



the concave plate of nervous matter which lines the 

 back of the camera-obscura, constituting the forward 

 portion of our organic optical apparatus. But the 

 silver retina at the back of the photographic camera- 

 obscura has the faculty of accumulating the impression 

 it receives ; and thus, by long exposure to an object too 

 faint to make a picture at once, either on a silver salt, 

 or on the rods and cones of the organic camera, the 

 continuously repeated throbs of otherwise obscure 

 radiations ultimately coincide to produce a visible 

 picture. Stars still fainter than the debilissima of 

 Herschel, below the sixteenth magnitude, and beyond 

 the reach of telescopic vision, have been revealed by 

 photography ; a nebula in the Pleiades, of which the 

 most powerful telescopes gave no indication, has been 

 discovered, and all have been accurately mapped. 



Leaping at a bound from the inconceivably great 

 down to the marvellously small, the photographic 

 retina applied to the eyeplace of the microscope 

 displays markings on the siliceous frustules of Dia- 

 tomaceas which the human eye similarly applied is 

 unable to see. Verily a new world is opened out 

 hereby. What mysteries of organic structure may 

 yet be revealed ? 



Photographs of Speech. — As an appendix to 

 the above, I may direct attention to a note presented 

 to the Academy of Sciences on January 18, by M. 

 Leon Esquille, who claims to have succeeded, by 

 means of the photophone, in fixing on a photographic 

 plate the modulations of the voice, afterwards re- 

 producing the words by the telephone, and projecting 

 in oxyhydric light the positive image of the plate on 

 Mercadier's selenium receiver. Such is the announce- 

 ment of this exploit given in "Nature" — vague at 

 present, and liable to the disappointments that have 

 befallen Edison's phonograph, that was very much 

 announced. A little time, however, will show to 

 what extent the expectations thus suggested may be 

 realised. 



Botanical Communism. — At the annual meeting 

 of the Association of German Naturalists, held at 

 Strassburg in September last, a subject of considerable 

 interest to students of natural history was discussed. 

 Several eminent continental botanists agree in affirm- 

 ing that a considerable number of phanerogams, 

 especially forest trees, do not draw their soil food 

 directly from the soil, but are clothed and fed by the 

 agency of an investing layer of fungus-mycelium, to 

 which the name of Mycorhiza has been given. 



The investing fungus is not a parasite, properly so 

 called, though it appears to feed upon the rootlets it 

 clothes. There is a mutual dependence, an equitable 

 giving and taking, going on between the root and the 

 fungus — that kind of friendly proceeding known as 

 symbiosis. In many of the cases named the coating 

 of fungus completely envelops the root, and is 

 especially well developed at its apex, the thickness 



