AERIAL EXPLORATION OF THE ARCTIC REGIONS. 219 



follow the naval traditions of the old British " sea-dogs" rsither than 

 those of our modern naval lap-dogs, and will not turn back after a 

 first struggle with the cruel Arctic ice, even though they should sup- 

 pose it to be " paleocrystic. " 



MR. WALTER POWELL. 



Scientific aerostation has lost its most promising expert by the un- 

 timely death of Walter Powell. He was not a mere sensational bal- 

 looner, nor one of those dreamers who imagine they can invent flying 

 machines, or steer balloons against the wind by mysterious electrical 

 devices or by mechanical paddles, fan-wheels, or rudders. 



He perfectly understood that a balloon is at the mercy of atmos- 

 pheric currents and must drift with them, but nevertheless he re- 

 garded it as a most promising instrument for geographical research. 

 I had a long conference with him on the subject in August last, when 

 he told me that the main objects of the ascents he had already made, 

 and should be making for some little time forward, were the acquisi- 

 tion of practical skill, and of further knowledge of atmospheric cur- 

 rents ; after which he should make a dash at the Atlantic with the 

 intent of crossing to America. 



On my part, I repeated with further argument what I have already 

 urged on page 113 of the Gentleman's Magazine for July, 1880, viz. the 

 primary necessity of systematic experimental investigation of the rate 

 of exosmosis (oozing out) of the gas from balloons made of different 

 materials and variously varnished. 



Professor Graham demonstrated that this molecular permeation of 

 gases and liquids through membranes mechanically air-tight, depends 

 upon the adhesive affinities of particular solids for other particular 

 fluids, and these affinities vary immensely, their variations depend- 

 ing on chemical differences rather than upon mechanical impermea- 

 bility. My project to attach captive balloons of small size to the roof 

 of the Polytechnic Institution, holding them by a steel-yard that 

 should indicate the pull due to their ascending power, and the rate 

 of its decline according to the composition of the membrane, was 

 heartily approved by Mr. Powell, and, had the Polytechnic survived, 

 would have been carried out, as it would have served the double pur- 

 pose of scientific investigation and of sensational advertisement for 

 the outside public. 



If the aeronaut were quite clear on this point could calculate 

 accurately how long his balloon would float he might venture with 

 deliberate calculation on journeys that without such knowledge are 

 mere exploits of blind daring. 



The varnishes at present used are all permeable by hydjoj.-en gas 

 and hydrocarbon coal gas, as might be expected, h priori, from the 

 fact that they are themselves solid hydrocarbons, soluble in other 

 liquid or gaseous hydrocarbons. Nothing, as far as I can learn, has 

 yet been done with silicic or boracic varnishes,* which are theoreti- 

 cally impermeable by hydrogen and its carbon compounds ; but 

 whether they are practically so under ballooning conditions, and can 

 be made sufficiently pliable and continuous, are questions only to be 



* Since the above was written I have made some experiments with a solution of 

 sholl^c in borax (obtained by long boiling, and hereby claim the invention of its 

 application to this purpose, in order to prevent anybody from patenting it. I shall 

 not do eo myself. 



