Mechanical Science. 405 



great pyramid is 4,000,000 cubic metres, its weight is about 

 10,400,000 tons, or 10,400,000,000 kilogrammes. The centre 

 of gravity of the pyramid is elevated 49 metres from the base 

 and taking 1 1 metres as the mean depth of the quarries, the 

 total height of elevation is 60 metres, which multiplied by 

 10,400,000 tons gives 624,000,000 tons raised 1 metre. Then 

 the total of the steam engines in England represents a power of 

 320,000 horses. These engines, moved for 24 hours, would raise 

 862,800,000 tons 1 metre high, and consequently 647,100,000 

 tons in 18 hours, which surpasses the produce of labour spent 

 in raising the materials of the great pyramid. 



3. Prize Question.— VJ^hen the nozzle of a blowing machine 

 is placed at a certain distance from that of the tuyere, a 

 stronger current of air is obtained than when both are placed 

 together, as is frequently done. This effect is produced by 

 various causes dependant on the elastic nature of the fluid in 

 motion, and of the surrounding atmosphere. The Society of 

 Sciences and Arts at Metz have founded the following prize 

 question on this experiment : " What are the changes neces- 

 sary to be made in the tuyere of blowing machines, to intro- 

 duce, in the most advantageous manner, the good effect indi- 

 cated above, or any other improvement for the rapid transmission 

 of air to greater or smaller distances." The prize is 300 francs, 

 and is to be adjudged in April, 1822. 



4. Prize Question. — The Royal Academy of Sciences of 

 Toulouse has proposed as the subject of prize essays, " A 

 physico-mathematical theory of drawing and forcing-pumps, 

 stating the ratio between the moving power and the quantity of 

 water elevated ; attention being given to all the obstacles 

 which the force has to overcome." Among these obstacles are 

 enumerated, the weight and inertia of the column of water, its 

 friction against the tubes, its contraction at the apertures of the 

 valves, the weight and friction of the pistons, the weight of 

 the valves, the inequality between the upper and lower surface 

 at the moment the pressure opens them, &c." The papers are 

 to be written in French or Latin, and sent in before May, 1823. 

 The prize is a gold medal of 500 francs value. 



5. Lithography. — An experiment has lately been made to 

 take ofT impressions from plants by lithographic printing. A 

 specimen of Sibthorpia Europaa, which was gathered several 

 years ago in Cornwall, was covered with lithographic ink and 

 impressed on a stone, from which stone several impressions were 

 afterwards taken. The experiment was not so successful as 

 was wished, but still promised to be beneficial in leading to 

 the moans f>f multiplying copies of the impressions of plants. 



