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"tact with the air, has no action on lead. If the water contains the customary gases in solution, the surface of the metal freshly polished becomes quite dull and white. But if the surface of the water be not at the same time exposed to the air, the action comes to a close. When the air, on the other hand, is allowed free access to the water, a white powder appears in a few minutes on and around the lead, and this goes on increasing till, in the course of a few days, there is formed a large quantity of white matter, which partly floats in the water or adheres to the lead, but is chiefly deposited on the bottom of the vessel. In 12 ounces of distilled water contained in a shallow glass basin loosely covered to exclude the dust, 12 highly polished lead rods, weighing 340 grains, will lose 24 grains in 8 days, and the lead will then show evident marks of corrosion.” In page 534, Pro fessor Christison sums up the whole inquiry thus :—“ The gene ral results of the preceding inquiries are that rain or snow water for culinary use should not be collected from leaden roofs, nor preserved or conveyed in lead ; that the same remark applies to spring waters of unusual purity.” Dr. Brande, in Iris standard work on “ Chemistry ” (p. 833) says, on the whole question of the action of water soft and hard on lead, “ In distilled water free from air and in close vessels a clean surface of lead remains bright, but, under the same circumstances, m open vessels it soon tarnishes, small crystalline scales of oxide of lead are formed, a portion of which dissolves in water, and is again slowly preci pitated in the form of carbonate. In this case the oxygen is im parted by the air held in solution in the water. The film of oxide thus formed is soluble, to a small extent, in the pure water, and is thrown down in proportion as it passes into the state of carbonate. A very minute trace of sulphuric acid or of a soluble sulphate in the water entirely prevents this corrosive effect, and hence it is that common spring water is kept with considerable impunity in leaden cisterns, which, however, should have wooden and not leaden covers. In the latter case the vapour of the water below condenses upon the cover, and often tends to its rapid corrosion, it being, in fact, distilled water, and not, therefore, prevented in its action by any saline matters. So that, when water is to be kept in this way, as it generally is for domestic use, its qualities should be cautiously inquired and ex amined into, as very deleterious effectshave occasionally arisen from the solution of the oxide.” In the evidence given before the General Board of Health it was stated that some fatal accidents have been occasioned by the fall of leaves in leaden gutters and cisterns, the infusion of which appears to have caused powerful decomposition. You will see, gentlemen, that from the foregoing extracts, Professor Christison and Dr. Brande consider that it is dangerous to keep jrare water in lead cisterns under ordinary circumstances, at the same time they admit, under the conditions before described, pure water has no effect on lead. On the other hand, Dr. Lyon Playfair asserts that “All his experiments tend to prove that per fectly soft water has no action on lead, and that all the solid ingre dients of water tend to produce and increase the action of lead.” I must, however, tell you that the experiments above referred to were made with slips of lead inserted in bottles containing pure and other kinds of water and sealed up. To my mind the latter fact robs the experiments of their practical value, because we could not construct sealed up cisterns, and must, therefore, have our materials placed under different circumstances to those as above described, and probably arrive at different results. In concluding this portion of the subject, I feel that space will not permit me to do it that justice that its importance demands. To those who would wish for more information on the action of water on lead, I can refer you to the articles before mentioned.* It need scarcely be remarked that lead must not be laid on wainscot boarding. The lead covering to the roof of the new library in Lincoln’s Inn Fields was removed, and slate sub stituted. The spire of Notre Dame de Chalon, Chalon-sur-Mame, has figures in the face of the lead covering. These were formed by using tin, and Mr. Burgessf describes the process of tinning thus, “ The lead being first of all covered with a tolerably thick coat of lamp-black and size, and the pattern traced with a point. All that part of the surface to be tinned is removed with a share hook so as to leave it quite clean and bright; a little sweet oil is * Vide Builder, vol. x., pp. 59, 139. t See Builder, Vo], 14, pp. 409, 418, Paper on ^Ornamental Lead Work by Mr, Burgees. then rubbed over, and the solder applied and carefully spread with a copper bit in the usual manner.” A plumber who really understood his business should be able to cast lead into sheets even as thin as 41b to the foot superficial In casting sheet lead, a copper is provided, well fixed in masonry at the upper end of the workshop, near the mould or casting table, which consists of strong deal boards well jointed together, and bound with bar iron at the ends. The sides of this table, of which the shape is a paralellogram, varying in size from 4 to 6 feet in width, and from 16 to 18 feet and upwards in length, are guarded by a frame or edging of wood 3 inches thick, and 4 or 5 inches higher than the interior surface, called the shafts. The table is fixed upon firm legs, strongly framed together, about 6 or 7 inches lower than the top of the copper. At the upper end of the mould nearest the copper a box called the pan is adapted in its length to the breadth of the table, having at its bottom a long horizontal slit from which the heated metal is to issue after it has been poured in from 'the copper. This box moves upon rollers along the surface of the rim of the table, and is put in motion by means of ropes and pulleys fixed to beams above. While the metal is melting, the surface of the mould or table is prepared by covering it with a stratum of dry and clean sand regularly smoothed over with a kind of rake, called a strike, which consists of a board about 5 inches broad, and rather longer than the inside of the mould, so that its ends which are notched about two inches deep, may ride upon the shafts; this being pressed down the whole of the table reduces the sand to a uniform surface. When this is done, the pan is brought to the head of the table close to the copper, its sides being guarded by a coat of moistened sand to prevent its firing from the heat of the metal which is emptied in with ladles from the copper. These pans or boxes are made as to their contents equal to the quantity of lead required to cast a whole sheet at one time, and the slit is so adjusted as to let out during its progress along the table just as much as will completely cover it of the thickness and weight per foot required. Everything being thus prepared, the slit is opened, and the box is moved along the table dispers ing its contents from the top to the bottom, and leaving in its progress a sheet of lead of the desired thickness. From this description it will be understood how the old lead cisterns, fast disappearing, were cast. The pattern required for the front and ends would be impressed in the sand, and when cast the sheet of lead would thus be ornamented, and being bent at certain points at right angles the cistern would be formed. The great objection to cast lead is that it frequently happens in casting that small air holes are left through which water will of course find its way. This difficulty is overcome by milling the lead. Milled lead being now nearly always used I will supposed that is the mate rial with which we shall work in laying our gutters, flats, and flashings, I will not describe the thickness of the various -weights of milled lead at per foot superficial, but would advise all students to acquire by experience the power of testing, with the aid of the thumb and finger only, the several weights of milled lead, and, as a rule, dont believe too readily in heavy 41b lead when it ought to be 51b. In using milled lead for gutters, flats, and flashings, let the leading principle be that of giving the metal as much liberty as possible to expand and contract as it may be necessary according to the variations of the temperature: this is done by dividing flats into narrow strips by using rolls which should not be more than 2-6 apart. Gutters should not be more than about 10 feet long without .having drips or rolls, as may be necessary. In ordinary gutters the lead should always be at least 9 inches under slates, and 6 inches against vertical walls, and be properly flashed. The flashings should be well -wedged and pointed to brickwork and burnt into stonework. This latter plan is not done so often as it should be ; a groove or chase is cut into the stone, the edge of the flashing is then inserted, a length of clay, properly prepared, is attached, and molten metal poured in such a way as to make the edge of the flashing and the metal poured in, one solid mass. I would suggest the greater use of snow boards. As a rule the architect lias not the power of specifying heavy lead for gutters, and the result is, that after men have been employed to remove the snow from them on two or three or more occa sions, the lead is found to be cut into holes by the nails in the boots of the men so employed: the snow boards not only pre vents this, but secures a place underneath, in which the snow when thawn may pass rapidly away. The sides of dormers being vertical, have to be secured at one or more of the edges