All the kinds before named partake of a similar mode of laying, in as far as refers to the bonding or lap of one por tion of the slate over another. The lap of each joint is gene rally equal to of the length of the slate, and the slater selects all the largest of the description about to be used, to be put on nearest the eaves. W hen the slates are brought from the quarry, they are not so square as to be immediately fit for use, but are prepared by cutting and sort ing. The slater, to effect this, picks and examines the slate, observing which is its strongest and squarest end. He then, by holding the slate a little slanting upon, and projecting about an inch over the edge of a small block of wood, seating himself at the same time on something which is equal to it in height, cuts away straight one of its edges : next, with a slip of wood, he gauges the other edge parallel to the same, and cuts off that also ; after which he turns it round and squares the end. The slate is so far prepared, excepting it be the turning of his tool round and pecking through it, on its opposite end, two small holes, which arc made for the nails to enter when he lays it on the roof. All the quarry slates require this preparation from the slater. All slates are put on with nails or screws, and two, at least, are assigned to each slate. The copper and zinc nails, or iron nails tinned, are esteemed the best, as being less susceptible of oxidation than those of bare iron.
The preparation necessary for laying slates on roofs, con sists in forming a base or floor fur the slates to lie compactly and safely upon. For the doubles and ladies, boarding is essential, if it be expected to have a good water-proof cover ing. All that is required in the boarding for such slates is, that it be laid very even, with the joints close, the boards being properly secured by nailing them on the rafters.
When the boarding is ready, the slater examines it, and provides himself with several slips of wood, called tilting fillets. A tilting fillet is made about two inches and a half wide, tbrce•quarters of an inch thick on one edge, and cham fered away to an arris on the other. These fillets he care fully lays and nails down all round the extreme edges of the roof, beginning with the hips, if any, and, if not, with the sides, eaves, and ridge. When these are all done, he pre pares for laying the slates, and begins at the eaves first. For these he picks out all the largest slates, and places them regularly throughout, setting their lower edges to a line ; after which, he secures them by nailing them down to the boarding. lie then selects such slates as will form the bond to the under sides of the eaves. This part of the work con sists in placing another row of slates under those which he has previously laid, so as to cross and cover all their joints; such slates are pushed up lightly under those which are above them, and are seldom nailed, but left dependent for their support on the weight of those above them, and their own weight on the boarding. The countesses, and all other descriptions of slates, when intended to be laid in the best manner, arc also laid on boards. When the slater has finished the caves, he strains a line on the face of its upper slates parallel to its outer edge, and as far from it as he deems sufficient for the lap of those slates which he intends shall form the next course, which is laid and nailed even with the line, and crossing the joints of the upper slates of the caves. This lining and laying of the slates is continued till the slater gets up close to the ridge of the root; observing throughout to cross the different joints by the slates he lays on, one above another. This method is uniformly followed
in laying all the different kinds of slates, excepting whatare called the patent slates, as will be hereafter explained. All the larger kinds of slate are found to lie firmly on what are called battens, in consequence of which they arc frequently made use of for the sake of economy, being cheaper than the smaller slates laid on boarding. A batten consists of a nar row portion of deal wood, about two inches and a half, or three inches wide ; three of which are commonly taken out of a deal. When countesses are to be laid on, battens of three-quarters of an inch in thickness will be an adequate substance for them ; but for the larger and heavier kind of slates, inch battens will be necessary. When a roof is to be battened for slates, the slater himself is the best perSon to fix them, as they are not placed at a uniform distance from each other, but so as to suit the lengths of the slates ; and as these vary as they approach the apex or ridge of the roof, it follows that the slater himself becomes the best judge where to fix the batten so as best to support the slates.
The patent slating, as it is called, consists in selecting the largest slates, and those also of uniform thickness. A roof to be covered with this kind of slate, requires that its com mon rafters be left loose upon their purlins, as they must be placed so as to suit the widths of the slates, it being neces sary to have a rafter under every one of their meeting joints. Neither battening nor boarding is required for these slates, and the number of rafters will depend on the width of the slates; hence if they are of a large size, very few will be required, and of course a great saving in the timber takes place, besides giving much less weight upon the roof. The work of covering by this kind of slating is commenced, as before, at the caves, but no crossing or bonding is wanted, the slates being uniformly laid, with each end reaching to the centre of a rafter, and they arc all butted up to each other throughout the length of the roof; the rafters being so placed as to come regularly under the ends of two of the slates. When the eaves course is laid, the slates composing it are all screwed down by two or three strong inch-and-a-half screws at each of their ends into the rafters. A line is then strained about two inches below their upper edge, this being allowed as a lap for the next course of slates, which is laid on above, with its edges straight with the line ; and this lining, laying with a lap, and screwing down, is continued till the roof is finally covered. The joints are then to be secured by fillet ing, which consists in covering all the meeting joints with fillets of slate, bedded in glazier's putty, and screwed down through the whole into the rafters. The fillets are usually about three inches wide, and as long as the slate they are intended to cover. They are solidly bedded in the putty and their intersecting joints are lapped as those of the slates; one screw is put in each lap, and one in the middle of the fillet. The fillets, being so laid, arc neatly pointed up all round their edges with more putty; and are lastly painted over the colour of the slate. The hips and ridges of such slating are fre quently covered by fillets in a similar way, and have a very neat effect. But lead is the best covering for all hips and ridges of roofs, and it is not much dearer than covering them by this mode.