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acid angle of incidence apparent magnitude appear atmosphere attraction axis bodies boiling Book cafe cause Chap clouds cold colours common concave concave mirror conductor consequently converge convex lens convex surface cylinder degree of heat direction distance diverging rays earth effect electric fluid electric matter electrified emitted equal experiments fire or heat force glass greater inches inflammable inflammable air interfection iron lens lever magnet matter of fire medium melted mercury metal mirror motion nature nitrous nitrous acid object observed optical oxygen parallel rays particles passing perpendicular phenomena phial philosophers phosphorus placed plane Plate pole principles produced proportion pullies radius rays of light reflecting surface reflexion refraction refrangible rendered retina screw seen sensible heat specific gravity spherical spherical reflector substances supposed telescope temperature thermometer tion tube vapour velocity vessel weight wheel wind
470 ページ - I saw from the southeast a haze come, in colour like the purple part of the rainbow, but not so compressed or thick. It did not occupy twenty yards in breadth, and was about twelve feet high from the ground. It was a kind of...
467 ページ - ... majestic slowness ; at intervals we thought they were coming in a very few minutes to overwhelm us; and small quantities of sand did actually more than once reach us. Again they would retreat so as to be almost out of sight, their tops reaching to the very clouds.
348 ページ - ... over a large tract of country, the lightning is seen to dart from one part of it to another, and often to illuminate its whole mass. When the cloud has acquired a sufficient extent, the lightning strikes between the cloud and the earth, in two opposite places; the path of the lightning lying through the whole body of the cloud and its branches. The longer this lightning continues, the...
462 ページ - The harmattan comes on indiseriminately, at any hour of the day, at any time of the tide, or at any period of the moon, and continues sometimes only a day or two, sometimes five or six days, and it has been known to last fifteen or sixteen days.
256 ページ - B. in their way they form that extremity of the image at b. In like manner the rays E which come from the top of the object AB and fall parallel upon the great mirror at F, are thence reflected converging to its focus...
263 ページ - The axis of the prism (that is, the line passing through the middle of the prism from one end of it to the other end parallel to the edge of the refracting angle) was in this and the following experiments perpendicular to the incident rays.
328 ページ - C, standing on the floor, both appear to be electrized; for he, having only the middle quantity of electrical fire, receives a spark upon approaching B, who has an over quantity ; but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger, because the difference between them is greater. After such touch there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality.
470 ページ - I scarce could turn to fall upon the ground, with my head to the northward, when I felt the heat of its current plainly upon my face. We all lay flat on the ground, as if dead, till Idris told us it was blown over. The meteor, or purple haze, which I saw, was indeed passed, but the light air that still blew was of heat to threaten suffocation.
10 ページ - The idea of solidity we receive by our touch ; and it arises from the resistance which we find in body to the entrance of any other body into the place it possesses, till it has left it.
78 ページ - ... seconds, to roll down the incline. Thus this mechanical power is in proportion as the length of the plane exceeds its height ; and if a cask weighing 3 cwt. had to be rolled into a cart or part of a warehouse 4 feet high, and a plank 12 feet long was used, then a power of 1 cwt. would balance it, because the inclined plane is three times the perpendicular height. A slight power over the hundredweight would move the cask...
The Economy of Nature explained and illustrated on the principles ...
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