254 M. Berzelius on the Preparation 



ing, a man was pushed on so as to be forced to go two, three, 

 four, or more steps invohmtarily, as it may be called, at each 

 push ; or if he forced himself so to move by not exerting his 

 propelling powers, except at every second, third, fourth, &c. 

 time of taking up his leg from the ground. 



The advantage of skaiting, then, is in avoiding much of 

 that exertion which is necessary for moving the limbs among 

 themselves, and which has nothing to do with the propelling 

 force. 



The practical corollaries I have to draw from these obser- 

 vations are very curious. I have for many years been anxious 

 to realize them, but circumstances have forbidden me — they 

 are still but theories. I think I could show a mechanician 

 not only that the present mode of using animal power for 

 locomotion is very uneconomical, but that there is a better 

 mode feasible, and that that mode would be equally applica- 

 ble to machines where steam, &c. is the moving power. 



Z. A. 



XLII. On the Mode of obtaining Silicium, and on the Charac- 

 ters and Properties of that Substance. By M. Berzelius*. 



Decomposition of Fluatc of Silica by Potassium. 



WHEN we read the description of the experiments made 

 by MM. Gay-Lussac and Thenard on the silicated 

 fluoric acid and potassium, we cannot doubt that they decom- 

 posed the acid in the circumstances which they describe. 

 The potassium burns in the gas and condenses it ; a brown 

 matter is formed, which, boiled in water and dried, burns in 

 oxygen gas with the evolution of silicated fluoric gas, and 

 leaves as a residuum a white earthy matter. In applying my- 

 self to these researches, I looked upon the reduction of the 

 fluoric acid and of the silica as so certain, that I thought it 

 only necessary to examine the composition of the product ob- 

 tained, in order to exhibit the subject in a clear light. The 

 experiment of MM. Gay-Lussac and Thenard gave me the 

 same results as they obtained, with this difference; that the mass 

 when burnt in oxygen gas was not white, and that it had pre- 

 served its primitive colour without any remarkable change. 

 I expected to find some fluate of silica and potash, but the 

 concentrated sulphuric acid did not disengage any trace of 

 fluate of silica; and although carried to ebullition, it did not 

 produce any change in the substance. Nor was the substance 

 attacked by any acid but the fluoric, which separated the si- 

 * From the Aimalcs di- Cliimir ct de Pliys'iqjic, toni. xxvii. p. .'i3'. 



Ilea 



