344 
Professor Playfair’s Description 
Aar, and then into the Rhine. By this conveyance, which is 
all of it- in streams of great rapidity, the trees sometimes reach 
Basle, in a few days after they have left Lucerne ; and there 
the immediate concern of the Alpnach company terminated. 
They still continue to be navigated down the Rhine in rafts to 
Holland, and are afloat in the German Ocean in less than a 
month from having descended from the side of Pilatus, a very 
inland mountain, not less than a thousand miles distant. The 
late Emperor of France had made a contract for all the timber 
thus brought down. 
From the phenomena just described, I have deduced several 
conclusions, of which at present I can only give a very general 
account, without entering into any of the mathematical reason- 
ings on which they rest. 
“ 1. The rapidity of the descent is so extraordinary, it is so 
much greater than any thing that could have been anticipated, 
exceeding that of a horse at full speed, nearly in the ratio of 3 
to 2, that the account seems to tread on the very verge of pos- 
sibility, and to touch the line that divides between what may, 
and what cannot exist. The same question, therefore, I have 
no doubt, has occurred to many that occurred to myself, when 
I first heard of this extraordinary phenomenon. 
Is it possible that even if there were no friction, '’and if a 
body was accelerated along the line of swiftest descent, from a 
point 2500 feet above another, and horizontally distant from it 
by 44,009, that it could arrive at that lower point in three or 
even in six minutes ? This was the first question that occurred 
to me, and at a distance from books as I was then, and in no con- 
dition to undertake any nice or difficult calculation, I could only 
satisfy myself by a rude app;^oximation, that there was nothing in 
the reported circumstance that was without the limits of possi- 
bility. Had the result of the calculation been Contrary, I 
should not only have disbelieved the report, but I should have 
doubted the testimony of my own senses. 
From a more accurate calculation I find that if no friction 
nor resistance took place,, and if the moving body was allowed 
to take its flight in the line of the swiftest descent, that it would 
do so in less than sixty-six seconds. This is the minimum then 
time, and w^e may rest assured, while the laws of nature con- 
