On The Discoveries of the Past Half-Century Relating to Animal Motion

J. Burdon-Sandersonv
1881 Scientific American  
Upon a propel' arrangement, putting the bull's.eye and the instrument nearly in a line with the sun's azimuth, a superb representation of the double "tar, Castor, is seen, the faiuter star being that caused by intern al reflection. Intensely black diffraction rings round each, and several fainter ones, fewer as the quality of instrument:1tion is raised. Perfect roundness can only be attained by exact coincidence of the optical axes of the system. Very slight obliquity (even half a degree)
more » ... alf a degree) canses the rings to overlap and bulge on one si d e. Much obliquity gives rise to glorious curves of tire three orders of the conic sectio !ls, of wondrous beauty and preci sion in effulgent colo rs. Mercurial globules near the microscope exhibit very deli cate and complex forms when similarly miniatured, as minute solar disks, in sunligh t. Experiment,--An optician's gauge comprising half a dozen lenses of standa,rd foci )" to 1-6Uth, lying in the snnsbine, Illiniatur ed st:u'-disks by reflection (see 1 in figure), Inferior objective llZ' inch examined with fine power of 1,000 Two brilliant erilllS[)1l disks in contact expanding within focus to an oval ring of deep crimson beads. Ecpairnent,-If the ima ge of the sun be received on wbite paper from a small lens placed at varions degrees of obli quity peculiarly beautiful forms are seen fringed with color. \VlJen the lens is sufficiently minule these spectra exhibit to the microscope exqui sit ely arranged curves in jet-black lines; circular elliptic parabolic and hyperbolic, "'ith inex haust.ible variety, according to the focal plane of vision amI obJiq uity. Heliostatic star-disks most successfully exhibit these uniqne phenomena , The superiority of these pheno mena tn anything telescopic of the snrt is insured by the ab senee of atmospheric disturbance within so short a distance. Thl'Y are all under instantaneons control. The limits of human vision among so many bright puints are patent enough. So long as there is bright sunsbine every gl ittering point obscures, I might say utterly effaceil, the finer trareries of detail. A pa'sing clond,· however, bring'! them all out with astonisbi!lg fidelity , Brilliant dif fraction is thus demon strated to be incompatible with exact portraiture , The limit is reached in brilliant sunshine by the diffraction disks obl itemting the very objects which PI'O' duce Ihem. This limit is well measnred by the diameter of the smaller disks seen in contact, which in white compollnd light ge nerally appeal's by micrometric lIleasnrement to be between the 1-8LJ,000th and 120,000lh of an inch in the mi crnscopic field. We need not he snrprised at this variation: the undulatory theory of light gives one size only. Yet, as the spurious disk by theory it) shadpd off graduaUy inlo the first intensely black first ring, fainter stars telescopically show smaller disks , But while a close row of spurious disks are seen to coalesce and oblitemle themselves if too close, and become continuous as a thick I Llminous line-the necessary effect of brkht diffJ'ilctions-duller objects devoid of briiliance are seen of amazing minuteness of tracery. constructed that, with a consumption of 9 to 10 liters of I Pasteur Las discovered a safeguard against this plague, He water, it aspirates about 15 to 20 liters of air per minute, inoculates animals with the splenic virus artificially pre· and if it is connected with a reservoir of proper size, there! pared, or, to use his own phrase, "cultivated," He has will be obtained a blast of compressed air, which, when! found that by allowing certain intervals of time to elapse be issuing from a jet of 2 mm, in diameter, and with a wa ter· tween the impregnation of the ., virus·cultures" he can re&,u pressure of 2 to 3 atmospheres, equals a column of mercu ry late the strength of the poison, he can attenuate it till, of 22 cm . , and therefore is sufficiently strong to supply a instead of producing death, it acts, like the vaccine lymph large blast-lamp. among mankind, as a prophylactic against death. In his The complete apparatus consists, in general, of two main address before the International Medieal Congress, on portions; namely, the pump, B, and the reservoir, A. T he August 8, Professor Pasteur says: "I was asked to give a pump itself consists of th ree pieces, B, c, d, adjustable by public demonstration of the ref;ults obtained. Fifty sheep screws, of which the upper part, B, contains the upper cone were placed at my disposition, of which twenty-five were of the water-jd, and also the lateral tube, b, for conveying vaccinated , A fortni ght afterward the fifty sheep were the aspirated air. B is connccte,j with the stuffing-box, c, i noculated with the most virulent anthracoid microbe. The which may be screwed higher and lower, and in which the t . wenty-five vaccinated sheep resisted the infection, the tube, d, containing the lower cone, is likewise adjustahle by twenty·five unvaccinated died of splenic fever within fifty screw-thread. The pump is screwed, by means of the nut, hours. Since t. hat time my energies have been taxed to e, centrally upon the top of the reservoir, A, while its upper meet the dem ands of farmers for supplies of thi� vaccine , " end is connected by means of a rubher·tube, a a, with the I
doi:10.1038/scientificamerican12101881-4945csupp fatcat:7thegdfqtvhznfwe5m7dytbhhy