ON THE ATMOSPHERIC PHENOMENA OF LIGHT' 



[1852, 



ploi-eJ is the domain ol" Agricultural Science, that tlie raiiililer 

 amono- its novelties may iiud, without cncroaclimont, fruit and 

 flowere in abundance wherewith to enrich our store and ad\ance 

 the public good. 



To all who are interested in the objects of this journal we beg 

 ao-ain to state, that the progressive improvement and extension of 

 of the work will be commensurate with the support which may 

 be accorded to it by the public, and the degree to which the 

 Canadian Institute and the promotere of the Canadian Journal 

 may bo successful in soliciting and' combining the talents of tliose 

 classes to which they appeal. 



Indian Remains. 



NOTICE BY THE REV. C. DADE. 



The following account of a remarkable Indian burying ground, 

 which I visited soon after its discovery, may be interesting to 

 you, though, no doubt it has been thoroughly ransacked since, 

 and you may probably be acquainted with it. The spot is in 

 Beverly Township, and was then a part of the farm of Mr. Call, 

 ten or twelve miles from Dundas and two and a half from the 

 Guelph road. The burymg ground is situated on a ridge thickly 

 wooded with beech, maj^ile, &c., running east and west about a 

 mile, and bounded by a rivulet called the Dundas Creek. On 

 the summit I found several pits newl}"- opened, and a vast quan- 

 tity of human bones at the depth of about four feet. Among 

 the bones were iron tomahawks, brass kettles, pipes, beads, wam- 

 pum, conch shells, &c. 



1 brought home several specimens, and amongst the rest two 

 skulls, (the owner of one had evidently fallen by the blow of a 

 tomahawk,) a pipe elegantly formed of clay, a pipkin, &c. 

 There were three or four pits which had been opened beyond the 

 memory of the oldest settler. Trees were growing over tlie 

 graves of the same size as those in the surrounding woods, (one 

 beech being two feet in diameter.) It was thought tliat in the 

 eleven pits, at lea.st 2000 persons had been inten-cd ; in one of 

 the smallest pits a person counted 125 skeletons. I \'isited this 

 place in 1836. 



P. S. — A neighbour of mine, last year, ploughed up a copper 

 wedge, of the size and shape of common iron wedges used in 

 splitting rails, about a quarter of a mile from the lake. 



July 3rd, 18.52. 



On the Atmospheric Phenomena of Light: by J. Bradford 

 Clierrimaii, M. A., F. C. P. S., 



(Fellow of St. Johtiii College, Camhriilge, and Dep. Prof, of 

 Mathematics and Natural Pldlomphij in the Univcrsiiy of 

 Toronto.) 



Tiie atmosphere which surrounds theEarth possessesin common 

 with other ini|ieifoctly transjiarcnt media the property of modifying 

 tlie light which entei's it, in three distinct ways, namely, by absorp- 

 tion, transrais.sion and i-eflection, though in proportions whose 

 amount is not exactly determinable. Erom the exjierimonts of de 

 SausRure on the plains of Germany, this much seems demonstrated, 

 that, of the Sun's rays incident on tlic upper surface of the atmos- 

 pluTC, the Sun beingiii (liczeuitji and tlioskv ipiite clear, not more 

 llian twYHlliinlsrearh Ihe Knrtii, 111.', rest being either alisorbed or 

 relle<'ted. It is to this relleclion tliat we owe liiebliie e<il(iur of the 

 sky, tlie insensible grajation between day and niglit, and the dillii- 

 i^x\ light by which objects arc visible when notdircctlv illuminaled 



by the Sun's rays: without this, the shadow of every thick cloud 

 would involve us in absolute darkness, and the stars would be visible 

 all day, and at night appear as brilliant sparks in the midst of intense 

 blackness. The amount of absorption will be greater as the density 

 of the air which the ray traverses and the length of its path 

 increase, and from these arise the diminished briUiancy of the 

 Sun when on the horizon, and also the faintness of the light of 

 distant terrestrial objects and their coni;equent indistinctness. 



De Saussure has shewn by experiment that the blue rays of 

 the solar light are more reflected by the atmosphere than the 

 rest, and the red rays more easily tivansmitted ; thus, as the depth 

 and density of the .stratum of air increases the more will the blue 

 tint disappear and the le 1 predominate, as we see in the Sun at 

 its rising and setting. The blue tint is more decided in the 

 zenith than on the horizon where the colour of the sky is some- 

 times quite white, and the intensity of the blue increases as we 

 ascend from the earth ; at a certain height, the sky appears nearly 

 black. 



On the evening of a clear day as the Sun approaches the 

 horizon, the sky in his neighbourhood appears of a glowing red 

 or orange colour, extending along the western horizon, but dimin- 

 ishing rapidly towards the zenith and the east : at the same time, 

 in the point of the heavens opposite to the Sun, we often see the 

 same red tint prevailing, and attaining its greatest intensity just 

 at the instant of the Sun's sinking. Shortly aftenvards, below 

 this red part appears a circular segment of decided blue, the line 

 of separation being in general sharjaly defined : as the Sun sinks 

 lower, the red gradually disappears, and in the west is succeeded 

 by a briglit grey which fadas off as it meets the blue eastern seg- 

 ment. This latter is due to the shadow of the Earth projected on 

 the sky and coloured only by the blue diffused light; the grey, 

 which constitutes twilight, is due to the reflection of the Sun's 

 rays at the upper strata of the atmosphere by which we enjoy his 

 light when it can no longer reach us by direct transmission : it 

 deepens by degrees as the Sun sinks, and becomes altogetlier dark 

 when the Sim is more than 18° below the horizon. The duration 

 of twilight depends on the latitude of the place and the time of 

 year ; in the latitude of Toronto, the longest twilight lasts Ih. 36m. 

 at the summer solstice ; and the shortest, about 48 minutes, occurs 

 in the presentj-ear on Marcli .3rd and September 5th. In latitude 

 48 J° and .any place higher than this, t-svilight at the summer 

 solstice will continue all night 



Sometimes, but very rarely, when the Sun has set, there is seen 

 a pale glimmer extending upwards from him in a conical shape 

 towai'ds the north-west and reaching to a considerable height. 

 A fine instance was observed in the present year ; it is due, un- 

 doubtedly, to the light thrown on the sky by the strata of air 

 actually below the horizon and directly illuminated by the Sun's 

 rays. 



When a ray of light proceeding from an object passes obliquely 

 through a medium varying from point to point in density like the 

 atmosjjhere, its path is no longer a straight hne as in \acuo, but a 

 curve whose nature depends on the law of variation of the medium, 

 and as the direction in wliieli tin' oliject is seen is determined by 

 the direction of the ray on eiileiino- the eye, it lull.iws that the 

 places in which objects appear In lie are imt (he places tiny actually 

 occupy : the necessity of making an allowance for this gives rise 

 to one of the mo.st important astronomical corrections, called 

 Eefraetion. The eft'ect of this refraction is to raise all objects 

 \ertieally above their real places by an amount wliich is greater 

 as the object is nearer to the horizon:* thus the Sun's "disc is 

 completely visible to ns when he has sunk quite below the horizon, 

 and appears distorted in shape into a sensible o\al, the horizontal 



•It is recorilfi] liy a late Alricnn liavcller, llial in shooting on ihe sandy 

 deserts lliere, at tii-sl lie invai-ialilv lired loo liiali, ilic linds appealing miieh 

 above their red places from the uniisuallv sreal refi.ulion. 



