1886.] on Becent Besearches on Meteorites. 551 



The outer glass vessel serves to keep moisture from settling on the 

 sides of the etliylene tube. By means of the electric lantern and a 

 lens, an image of this part of the apparatus was projected upon the 

 screen, this being the first time that the experiment had been shown 

 on a large scale in public. 



Performing the experiment, the temperature reached was a little 

 below 200^ C, that is only 50° to 70'^ above the absolute zero of tem- 

 perature, and in the experiment about 5 lbs. of liquid ethylene were 

 employed. 



With reference to the main subject, the lecturer said that meteorites 

 came from regions of intense cold into our atmosphere ; most of them 

 weigh but a few ounces or pounds, but exceptional meteorites weigh 

 several hundredweight. A spherical body 3 feet in diameter, moving 

 at the rate of 18 miles a second at the height of 23 miles, where the 

 barometric pressure is only two-tenths of an inch, produces locally a 

 compression pressure 5600 times greater than that of the surround- 

 ing air. Descending vertically, it would pass through the whole 

 atmosphere in 15 seconds. The velocity stated in these data is 

 relatively low as compared with that of planetary bodies. Meteorites 

 travel at the rate of about 36 miles in a second. The velocity of a 

 shot from a 100-ton gun is about half a mile per second. 



Meteorites reach the earth covered with a thin and very remarkable 

 glaze, due to the fusion of their external surface during their brief 

 passage through the atmosphere. A velocity of 145 feet per second 

 in air gives an increase of 10° temperature, and the rate continues 

 as the square of the velocity. The surface temperature of a body 

 moving at the rate of 39 miles per second would reach 2,000,000°. 



The lecturer placed a piece of iron against a rotating emery 

 wheel, the friction of which caused showers of sparks to be thrown 

 out. These were so hot that some of the little globules of iron 

 composing them were fused into a plate of glass placed to catch 

 them. Great similarities exist between the flight of these globules 

 and the flight of meteorites, the heat and light in both cases being 

 partly due to friction and partly to chemical action. That chemical 

 action has an influence, he proved by applying oxygen gas to 

 the sparks, thereby causing them to burn more brilliantly, and by 

 applying carbonic acid to them, thus reducing their brilliancy. 

 When a piece of meteorite was applied to the emery wheel in place 

 of the piece of iron, the sparks were far less abundant, and of a dull 

 red colour. The glaze of meteorites can be imitated to some extent 

 by cooling a piece of meteorite to 20.0° C, and then dropping it for 

 a moment into the electric furnace; the temperature explains the 

 glazing of a meteorite, and that it has a motion of rotation must also 

 be considered in estimating the amount of friction, and therefore of 

 heat, to which it is subjected in its passage through the atmosphere of 

 the earth. An enormous amount of its energy, however, is expended 

 in heating the air, and aerial vibrations thus set up explain the noises 

 made by the passage of meteorites. 



