132

RETORTS.

mortar of iron-cement, without sulphur, is mixed with an equal weight of fire-clay, and spreadover the joint, which is then screwed up. The recesses for the bolts are filled up with thesame material. The centre joint, as also the joint of the cup at the back end, are preparedin a similar way, with the addition of a triangular groove cut in each part, as shown at V V,and a cement of sifted fire-clay is put between and thoroughly squeezed in.

It is found advantageous to allow the work some weeks to drv before the retorts areheated; and in letting down, while the fire is declining, all access of cold air and communi-cation with the chimney should be closed. A cement, recommended as well suited for thejoint of the upright pipe with the mouth-piece, is a mixture of whiting with half its weightof common salt mixed with water, into a plastic state, and applied like glazier’s putty.

The expenditure in renewing such an oven of three retorts is stated to be as under:—

Taking down old retorts and cleaning out oven ....

Three new retorts laid down at works ......

600 fire-bricks at 10s. . . . *

Fire-clay, tiles, lumps, etc. ........

Wages to bricklayer, fitting on mouth-pieces, building and setting inretorts, repairing flues, etc., about ......

Repairing bolts and screws, connecting with upright pipes ready foraction ...........

£. s. d.0 10 612 12 0a 0 0

1 5 0

2 2 6

1 7 6

Total cost of renewal . .... .£20 17 6

An oven of three such retorts will work from forty to forty-five weeks, including one or twodays per month lying oft' for cleaning, and produce on an average 95,000 cubic feet of gasper week from cannel coal. When let down two or three times the actual service was some-what less, but in one instance an oven was let down after having been in good workingcondition uninterruptedly for seventy-four weeks.

No specific data are supplied regarding the fuel required for heating these retorts; forthere being no market for the tar and a good demand for the coke, the whole of the tar wasconsumed in the furnaces, mixed with a cheap Scotch coal and the dross from cannel coalin its preparation for the retort. Though no positive account was kept of the cost of thefuel, it was estimated not to exceed that required for iron retorts. It is further remarkedin favour of this small setting of clay retorts, that they are usually clean on the outer surface,and when heated retain a more uniform temperature than iron, whilst the latter are liable toaccumulate a thick coating of carburet of iron, which causes a waste of heat, and acceleratesthe destruction of the iron by becoming a flux when subjected to intense heat.

The following is the description given by Mr. James Reid, of the Montrose Gasworks, ofhis setting of three clay retorts:—

“ We have had clay retorts in operation for the last three years, and from the great difference inprice, compared with that of iron retorts of the same size, and from the immense superiority overmetal in working them, we have entirely given up the use of the latter. I tried the clay retorts inthe shape of an ellipsis, in the D and circular form, and find the cylindrical to be the best adapted