504. A glance through the various engineering journals will give one some idea of their photographic requirements. All of the various trade journals make certain demands upon the photographer, but one of the most lucrative fields that the photographer can enter is the one embracing engineering work. It is always necessary to have photographic records of the various stages during the progress of any large engineering project, such as the photographing of canals, canal locks, subways, tunnels, buildings, the erection and installation of all kinds of machinery, etc. To illustrate the handling of subjects belonging to this class, we show in Illustration No. 98 four different views of the canal built on the Columbia River to overcome the rapids at the Cascades. The illustrations are intended to give an idea of the manner in which a canal lock is operated.

505. The object of canalizing rivers is usually to overcome abrupt ascents, and several short canals have been constructed for this purpose on various rivers in the United States. The width of these canals is governed, to a certain extent, by the size of boats that are to pass through them. They are, however, wide enough to allow of two boats passing in them, so that one may go up and the other down at one filling of the lock.

506. Figure 3 is a view taken from the rear of a boat having entered the first lock, and shows one of the lower gates as it is being closed. Figure 4 shows a lock filled with water, both of the gates having been closed, of course. The boat has been raised to the level of the water in the lock above. Figure 1 is a view from the front of the boat, showing the lower side of a closed gate, while Figure 2 shows this gate partly open, with a boat in the upper lock ready to come down to the lower lock.

507. This branch of commercial photography is inexhaustible, so far as the variety of subject material is concerned, for it is necessary to photograph all manner of building and engineering projects during the different stages through which they have to pass before completion. As many as twenty-five or thirty photographs are often required to show these different stages.

508. In Illustration No. 99 is shown the structural iron work of a large armory. This particular view was taken from the rear of the building, to give a general idea of the frame-work. At this stage it was possible - in fact desirable - to make six different views, for the work had progressed to different degrees in different portions, the masonry work on the front of the building having been completed. The engineers generally desire many detail photographs of different phases of the work which will show the methods of construction, and especially is this true when a new form of construction is being used.

509. The building of large reservoirs makes interesting photographs, and in Illustration No. 100 we show the completed masonry work which forms the dam of a large reservoir supplying water to a near-by city. The position chosen from which to make this view was one that shows the construction in a most perfect manner, and also gives an adequate idea of the dam and its general surroundings.