Miscellanies. 395 



with all hard bodies, such as copper, brass, zinc, glass, hard woods, 

 &c— Ann. de Chimie, tome XLH, p. 41.— Brewster's Journal, July, 

 1830. 



Hay 



In the sum- 



mer of 1827, a rick of hay, in the parish of Dun near Montrose, was 

 set on fire by lightning, and partly consumed. When the fire was 

 extinguished by the exertions of the farm-servants who were on the 

 spot, there was observed in the middle of the stack a cylindrical pas- 

 sage, as if cut out by sharp instruments. This passage extended 

 down the middle of the stack to the ground, and at the bottom of 

 it there was found a quantity of vitrified matter, which, there is every 

 reason to think, is the product of the silex contained in the hay which 

 filled up the cylindrical passage. The existence of silex in the com- 

 mon grasses is well known, and the color of the porous and vesicular 

 mass is very like that which is obtained from the combustion of sili- 

 ceous plants. We have been indebted for a specimen of the sub- 

 stance to Captain Thomson of Montrose, who examined the spot 

 almost immediately after the accident had taken place.— Brewster'* 

 Journal, July, 1830. 



11. Flying in the air.— On the 6th of September last, Gay-Lussac, 

 Flourens and Navier, made reports to the French Academy on the 

 memoir of De Ckabrier, relative to the means of travelling in the 

 air, and to a new theory of animal motions. The following are ex- 

 tracts. It is easy to compare the quantity of action which a man is 

 capable of producing, with that which is required for flying. The 

 bird which hovers in the air spends, at every movement, the quantity 

 of action necessary to raise its weight to the height of 8 metres, 

 While, in the same time, a man cannot raise his own weight, .086 me- 

 tres ; so that the quantity of action is only ^ part of that which the 

 bird exerts to support himself in the air. If man had the power to 

 spend, in as short a time as he pleased, the quantity of action which 

 he commonly spends in eight hours, we find that he might every day 

 support himself in the air during five minutes ; but as he is very far 

 from having that faculty, it is evident that he could only sustain him- 

 self for a much shorter time, and that this would be but a small frac- 

 tion of a minute. This approximation shows how chimerical are the 

 attempts made to render man capable of flying in the air. It being 

 impossible for man, and the greater number of quadrupeds to support 

 themselves in the air, it remains to be decided, what it is possible to 

 accomplish, when, by means of gas, lighter than atm< -phenc air, the 

 weight of a man is supported, and nothing more is necessary than 

 to move forward and direct the apparatus at pleasure. 



