TRACT 34.

IN GUNNERY.

29

foundation for a new theory of gunnery. It is rather difficultto obtain with accuracy such long ranges as our initial velo-cities would produce, being from 1 mile to 2 miles, whenthe projection is made at an angle of 45 degrees for insuch long ranges our small balls cannot be seen, when theyfall to the ground. We were obliged therefore to haverecourse to the water, in which the lall of the ball can bemuch better perceived ; because the plunge of the ball inthe water, breaking the surface and throwing it up, makesthe place visible at a great distance. But then anotherdifficulty occurs, how to obtain exactly the distance of thefall, or length of the range, as the mark made in the surfaceof the water is visible but for a moment. This difficulty,however,our situationat Woolwich, closeby theriverThames,enabled us to overcome, as well as afforded a good length ofrange. For, at our situation in the Warren, the river makesa remarkable turn, and forms below us the part called theGallions Reach, a map of which is here given in plate i.In this map, a denotes the point where the guns wereplaced, being the Convicts’ Wharf, which is sp called be-cause it is there that the convicts, or felons condemnedto work on the river Thames , land their gravel, and uponwhich they usually labour. From this point we have a con-venient range of about a mile and a half towards b, in thecounty of Essex, where there is a private or merchant’spowder magazine. The buildings near c consist of theacademy and a noble range of store-houses ; and from thispoint we should have had a still longer and more convenientrange, had not our view from hence been interrupted byfour large hulks, which lie, for the use of the convicts,in the river opposite the part between this point and thepoint a. Having found this convenient situation for ouroperations, we made an exact survey and map of the twosides of the river, both ways beyond the extent of the ranges;and fixed on convenient stations at D and e on the southside, and F and g on the north side of the river, to placeJuvo parties of observers, who might mark the place where