quare towers at the corners,
used as offices; the entire structure forming three sides of a square,
fronting two hundred and fifty feet along the canal, and extending back
two hundred and seventy-five feet. The north side was mostly a brick
enclosure with high walls, but having no roof, and temporarily used for
storing wood--its ultimate destination was for workshops.

Within the square were located the kilns for drying the wood to be
distilled in the charcoal retorts; the copper boilers and other
apparatus for the extraction of the saltpetre from damaged powder; as
also the arrangement for the final extraction of the saltpetre from the
refuse of the Refinery; lastly, the great chimney, into which all the
smoke flues of the entire structure terminated.

In the projection of this part of the Powder Works, I conceived the
design of making the central portion present the appearance of a grand
monumental structure. For this purpose the chimney was placed centrally,
and its exterior dimensions considerably enlarged; in fact, it is
composed of two distinct parts, the chimney and outside obelisk; the
former being enclosed at its base by a square tower, nineteen by
thirty-five feet in height, whose battlements arose to view above the
front walls. From the top of this tower the enveloping obelisk
commenced, and ascended one hundred and fifteen feet, making the
complete structure one hundred and fifty feet from the ground to the
coping. The interior chimney flue is five feet square from bottom to
top. The corner stone, or rather the box, containing the usual
documents, was, by a fancy of the architect, placed in one of the
corners of the top coping of the obelisk.

The saltpetre refinery occupied the right central portion of the front,
being sixty-five feet long, fifty-five feet broad and thirty feet high,
open from the floor to the ventilated roof. At the east end were four of
the large evaporating iron pans, placed side by side, and elevated three
feet above the floor by the brick work which surrounded them; five
similar pans were in a corresponding position at the west end, and the
large copper drying pans occupied forty feet along the north side at the
same height. Each evaporating pan had a separate furnace, and the heated
air from the whole passed beneath, and in contact with the bottoms of
the drying pans on its way to the great chimney; the furnaces opened
into side rooms communicating with the outside open space in the