Actually a LONG time ago I bought the Gun DIgest Treasury of 1964 (I was a kid at the time but I remember I got it on clearance, if I remember right at a Walden Books, in around 1969 or 1970 because in 1964 I was 6!
I know I still have it around somewhere in a box, but that was where I first read about the air rifle L&C had, and that it wowed the Indians as well as killed some game. This is not new research, historians have known about the air rifle since the expedition.
But the thing I remembered most about the article is that Napoleon had an entire unit of scouts armed with air rifles, they fired a fairly large caliber ball and in some battles his enemies threatened to execute any soldier caught with one. Kind of like the German's threatened in WWI with doughboys armed with shotguns.
There was no reports as to whether this happened, but they were reported to have a demoralizing effect on the enemy, it would be almost like having the very first silencers on a battlefield.
The article concluded that interest in air rifles continued in Europe, but for some reason it could not explain it was never again used in war, and why it did not gain popularity here.
The reservoir was a large Ball type made of Indian rubber that hung underneath about mid ships and was pumped up with a hand pump. Supposedly accurate, and powerful, and the seal design was actually quite modern in design, and only needed constant lubrication to keep from dring out.
I was amazed even back then!