His observation finds that "that the degree of spirality, the number of threads, or the depth of the channels, is not regulated by any invariable rule, but differs according to the country where the work is performed and the caprice of the artificer"
I believe that means that at the time the twist rate, number of grooves, or how deep they are, wasn't set by a fixed rule. It changed based on which country the work is done in and what the maker felt like doing.
He the describes "in some parts of Germany and Switzerland an improvement is made by cutting a piece of very thin leather or fustian (a type of heavy, durable fabric, historically made from cotton, linen, or a blend of both), in a circular shape, somewhat larger than the bore; this being greased on one side, is laid upon the muzzle with its greasy part downwards, and the bullet being place upon it, it is then forced down the barrel with it. The riflings should for this purpose be shallow, and the bullets not too large."
His observations include detailed study of loading abilities and the introduction and limited use of breech loading firearms and their benefits.
"We have had them also without any groove, as in the case of the elliptie bore (Lancaster's) or as in the hexagonal bore introduced by Whitworth (a celebrated engineer)."
He goes on to describe his background in testing weapons from many countries identifying England as the top producer in terms of quality and accuracy.
"The Kentucky rifle, usually of small internal diameter, will, it is true, work admirably up to perhaps 300 yards. The German rifles may be met with, of still larger bore, that will send a ball, with tolerable precision, considerably further, and the Swiss and Tyrolese (inhabitants of Tyrol, a historical region in the Alps that spans across modern-day Austria and Italy) having adopted cylindro-conical bullets are gradually extending and improving their practice; but as yet I am very confident that they are for the most part considerably behind us (England)."
"The rifling, known technically as the 'gaining' or 'gathering twist' is said to be of American origin." He goes on to bash it
"Having tried numerous rifles on this plan, I quite concur with General Jacob in his condemnation of the system, and would recommend no one again to waste money by experimenting in this direction. The principle in question is obviously unphilosophical, for, besides altering the shape of the bullet, it causes increased resistance at the muzzle, the very place where relief is wanted."
I sense much anti-American sentiment and we're only on chapter one. I suspect they were correct but I think this is the perfect point to shift gears and see how this quote holds up today.