THE ADDRESSES, LECTURES, ETC., OF 



I should have wished that in writing on the subject he had been 

 in possession of the whole of my argument. 



Dr. Tyndall is not only one of the most prominent men of 

 science, but has gained fame also in the Alps and elsewhere for 

 his power of physical endurance, of which his letter under acknow- 

 ledgment furnishes another striking proof in that he was able to 

 hold his breath for nearly 90 seconds, whereas 60 seconds is the 

 utmost coral fishers are said to be able to endure without 

 inhalation. 



We have heard of late of gentlemen swimming across the 

 Channel, and of others crossing it in a balloon, to which feats 

 others, acting on Dr. Tyndall's suggestion, may add that of going 

 across from shore to shore, protected by a Fleuss-dress, through a 

 tunnel filled with carbonic acid. But I imagine that after 

 these adventurous spirits have accomplished their respective feats 

 they will be more inclined to indulge in the good things offered at 

 the Lord Warden Hotel than in schemes of taking this country by 

 assault. Dr. Tyndall's allusions to the means that might be at 

 the disposal of the enemy of ridding the tunnel of carbonic acid 

 as fast as it could be poured in, require, of course, serious con- 

 sideration, and had not escaped my attention in maturing my 

 scheme. Assuming a certain rate of flow of carbonic acid into the 

 tunnel at the point of its greatest depression, and where it would 

 lodge, owing to its superior specific gravity, I ascertained by a 

 simple calculation. that if even 1000 horse-power were employed 

 at either end of the tunnel in causing a current of air through the 

 same, the other being left open to facilitate the operation, the 

 frictional resistance encountered in a channel of such length would 

 be such that the accumulation of carbonic acid in the depressed 

 portion of it could be readily maintained for 30 days, by means of 

 such continuous inflow as I contemplated. The chambers in which 

 the carbonic acid would be generated being inaccessible to the 

 enemy, such a continued inflow would, I maintain, form an 

 effectual barrier to a hostile host, and to increase the pumping 

 capacity to more than 1000 horse-power would require such 

 elaborate installation as would only be the work of time. 

 I am, Sir, your obedient servant, 



C. W. SIEMENS. 



12, QUEBN ANNK'S GATE, WKSIMINSTER, May 6, 1882. 



