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It was on the N.N.W. side of the hill; so that it was sheltered from the heat every day, till it came to a W. and by S. sun, or thereabouts, which, in those countries, is near the setting. Before I set up my tent, I drew a half-circle before the hollow place, which took in about ten yards in its semi-diameter from the rock, and twenty yards in its diameter, from its beginning and ending.
Let there be described on Qq a semicircle cutting the ray CR at B, from which BV is drawn perpendicular to Qq; and let the proportion of the refraction for this section be, as before, that of the line N to the semi-diameter CQ.
A minute later Worsley saw a golden glow, which expanded as he watched it, and presently the sun appeared again and rose a semi-diameter clear above the western horizon. He hailed Crean, who from a position on the floe 90 ft. below the crow's- nest also saw the re-born sun. A quarter of an hour later from the deck Worsley saw the sun set a second time.
The comets also must be a delectable residence; that of 1680 completing its orbit in 576 years, and being at its greatest distance about eleven thousand two hundred millions of miles from the sun, and at its least within less than a third part of the sun's semi-diameter from its surface . They must therefore have delightful vicissitudes of light and the contrary; for, as to heat, that is already provided for.
Draw the transverse centre line, answering to the centre line of the crank shaft, on the sole plate of the engine, or on the cylinder mouth if the engine be of the direct action kind; describe a circle of the diameter of the crank pin upon the large eye of the crank, and mark off on either side of the transverse centre line a distance equal to the semi-diameter of the crank pin.
And it should be known that it is none other than that curve which is described by the point E on the circumference of the circle EB, when that circle is made to roll within another whose semi-diameter is ED and whose centre is D. So that it is a kind of Cycloid, of which, however, the points can be found geometrically.
Similarly, if one considers some other point of the wave IK, such as h, it will go along hm, parallel to CI, to meet the surface IB, while the point K traverses Kl equal to hm; and while this accomplishes the remainder lB, there will start from the point m a partial wave the semi-diameter of which, mn, will have the same ratio to lB as IA to KB. Whence it is evident that this wave of semi-diameter mn, and the other of semi-diameter IA will have the same tangent BA. And similarly for all the partial spherical waves which will be formed outside the crystal by the impact of all the points of the wave IK against the surface of the Ether IB. It is then precisely the tangent BA which will be the continuation of the wave IK, outside the crystal, when the piece K has reached B. And in consequence IA, which is perpendicular to BA, will be the refraction of the ray CI on emerging from the crystal.
All the reflexions of those rays which fall upon the quarter-circle AB will touch a curved line AFE, of which line the end E is at the focus of the hemisphere, that is to say, at the point which divides the semi-diameter BD into two equal parts.
I found also the value of CG the semi-diameter parallel to the tangent ML to be 98,779. Now passing to the investigation of the refractions which obliquely incident rays must undergo, according to our hypothesis of spheroidal waves, I saw that these refractions depended on the ratio between the velocity of movement of the light outside the crystal in the ether, and that within the crystal.
Which wave is here represented by the circumference SNR, the centre of which is A, and its semi-diameter AN equal to CB.
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