1869.] Drainage. 657 not be less than brick thick, unless, in- deed, the required sewer happens to be verjr small. They are constructed of common brick, of good hard qualit r , in lime mor^ tar, with the exception of the invert, which is jointed with pure cement mortar. Radiated bricks should be expressly manufactured for sewer building, as the joints of ordinary brick are necessarily too open at one end, and, consequently, make but a poor job at best. The rate of inclination must be a sub- ject of mature consideration. The greater the fall, the more intense the velocity, is the governing rule, and this, of course, includes the perfection of the scour. Give the greatest rate to the house-drains ; the next rate to the pipes with which they are to be immediately connected ; and so on, diminishing the rate gradually as you get towards the outlet. The reason for this is obvious ; for, in the first place, your main object is to remove the sewerage from immediate proximity to' the houses, so that perfect drainage is of less consequence at a dis- tance than it is in the houses themselves. But, beyond this, there is another more important object in such arrangement, for as the body of water is less in the drains or sewers more remote from the outlet, it is more likely to be sluggish in its movements than where there is a large volume of water, and this tendency to sluggishness is overcome by an in- creased rate of inclination, so that the want of velocitjr caused by the small body of water in the lesser sewers is compensated by the extra fall, and thus the flow in all cases is rendered equal, or very nearly so. Ventilation is a very necessary sub- ject as applied to sewers ; especially main sewers, through which, at times, men may have to pass. We would always recommend air shafts to be con- structed at a good sharp inclination from the crown of the arch of the main sewer to the gutter at the sidewalk, and if this is done at the corners of streets, these air-ducts, or ventilators, will also answer for street surface drains. This practice is now well understood, and. until some better one is devised, it is to be hoped that it will never be neglected. Thus much, at present, on the subject of Drainage; one of so much imminent consequence to the health of every com- munity, that on its observance rests the responsibility which every conscientious man incurs, who undertakes so impor- tant a work. Fell. — We have some poor building done on this side of the Atlantic occa- sionally, but we have not yet had the mortification of chronicling, in this ad- vanced nineteenth century, anything like that which we find in the London Builder, namehy, the fall of two houses at Liverpool, which were "topped out at three stories high. The basement walls were nine inches thick ! and from the ground-line to the top were but four- and-a-half inches thick! These walls, carrying the joists of the three floors, buckled up, like a sheet of paper, and fell. The wonder would have been great had they stood. Their fall was well deserved, and to be rejoiced at ; were it not that, by it, four poor men were killed. Another Aid. — Joinery has gained much by mechanic invention. The planing-machine not alone relieved the workman of an immense amount of drudgery in the way of smoothing boards, but it likewise tongued and grooved them in the truest, as well as speediest manner. Scroll-sawing did great things for him ; and now he 1ms an aid more admirable still, in the dove- tailing machine, which at once rids him of a very harassing operation, difficult to perform in. a truly workmanlike man- ner, and worthless if not done so. We are glad to see that this latter machine is so completely successful, doing its work as perfectly as any other Yankee notion.
