"But you will study the manifold details of roofing when the men are at work, for labour of this kind requires minute care. We have to struggle with a subtle foe - water. It discovers every interstice, and takes advantage of the least negligence to make its inroads; and so much the more since, driven by the wind, it acquires a power and an activity which it would not possess if it fell vertically, like properly-behaved rain. So in climates where showers are gentle and fall only in calm weather, the roofs are simple, and do not require the innumerable precautions demanded among ourselves; and that is why I adopt the plan of securing the slates with hooks. Here the westerly and north-westerly winds are violent, and drive the rain and snow under an angle of 30°. Slates held only at the top do not lie close, and tilt up at their outer extremities, and the rain and snow soon get in. That is also the reason why we have given our roofs an angle of 6o°; for the rain, when violently driven, generally descends perpendicularly to this inclination, and there is then no danger of its getting under the outer extremity of the slates.
"The arrangement of the gutters also requires great attention. Their channel should have a sufficient inclina tion - say an inch in a yard - to ensure thorough clearance; but each length of lead or zinc forming the channel should have a drip - a slight step of iI to 2 inches - that the water may not find its way under the joints. These re quirements necessitate our giving to the gutters a sufficient depth to get these falls from the culminating points to the discharges, or down-pipes, and that these pipes may not be too far from each other, so that the water may not have too long a course to make. Besides this, we should contrive on the front of the gutters, issues, or small spouts for over flows, so that if the snow or ice should encumber the orifices of the down-pipes the water may run off. It is, moreover, desirable to give the back of the gutter a greater height than the front, that the water may in no case get inside. This, then (Fig. 6i), is the section we shall give to our gutters. The stone course, A, behind the gutter being i6 inches high, the board which forms the front of the gutter shall be 13 inches. You remember that upon the cornice-table we left a slope forming a hollow between each joint, to ventilate the bottom of the gutter and to ensure the escape of the water in the event of an overflow. Our gutter, then, will consist of an oak board, B, forming the bottom, of a side, C, forming the front, and of a roll or bead fastened on the top edge of the front. This front board is to be slightly inclined, that the lead lining may have less tendency to give down.
"The eaves of the roof being at D, our lead lining shall be fastened at E by nailing, follow the section of the gutter, and be doubled over at its edge, G. We shall cover the
front with another sheet of lead, also doubled over at its top and bottom edges, H I, with clips of zinc screwed to the board. This lead covering of the front will be held by screws, whose heads must be covered with little caps, a, soldered over; then a roll, K, will cover the bead and fold under the doubled edges, G and H.
"But previously, the bottom and fronts of the gutters will be attached by means of angle-irons, sunk-in flush, and which are let into the wall at the bottom of the course, A. These angle-irons will come on the outside, and not on the inside of the gutter. At regular distances, in the gutter-front, we shall bore the holes for the little spouts, M, which serve as overflows.
"The down-spouts, placed in the angles of the building, will pass, at their upper orifice, through an opening con trived in the cornice, as shown by the detail, N. A funnel of lead will connect the bottom of the gutter with the ori fice of the cast-iron down-pipe, and will be soldered, of course, only to the bottom of the gutter, resting loose in the part which enters the down-pipe.
"In order to obtain the necessary falls in the bottom of the gutter, we shall run in a thickness of plaster, with stops of wood for the drips at the end of each length of the lead lining, as you see at 0. These sheets of lead should not exceed 10 feet each in length.
"The ridges of the roofs and dormers shall also be of lead doubled and folded, as shown by the sketch, P. Two strips of lead, b, are first nailed on to cover the slate, d; then the upper half of these strips are rolled and folded into the sheet, i, which covers the ridge roll. This last piece of lead is, besides, held by screws, whose heads are covered by a bit of lead; thus there is no danger of its being displaced by the wind.
"I describe to you here only the principal points in the roof-plumber's work, which requires very great judgment and extreme care. You will be able to study it practi cally in detail when we have good plumbers at work. Some of the Parisian plumbers possess remarkable skill. They will also attend to the arrangements for the supply of water in the house - the water-closets, baths, &c. But I have an important piece of advice to give you : Lead laid on oak that has not been steeped in water oxidizes very rapidly. The acetic acid which this kind of wood contains changes the sheets of lead placed on it into ceruse in a few months, especially if the wood is not sufficiently ventilated on the opposite side. I will therefore point out to you the only kinds of wood that should be employed for the gutters and ridge rolls. We will take old wood from the remains of the old mill, which when cut up will be in the condition required, for this wood has long ago dis charged its sap.