The underback R R, which is placed between the 8 iron columns, upon brickwork, supported upon bearing piles, is formed of cast iron plates, united by screws, in the same manner as the mash tun, and as is explained in the Figures. The plates arc flat on the inside, but have Haunches all round the outside, and ribs across to strengthen them. This is shewn by representing part of the plates as removed. The wort is drawn off from the mash tun, by 8 cocks in the bottom, two of which are shewn at St, lig. 2. They allow the wort to flow into the underback, whence it is drawn by a pump, the suction tube for which is marked 'I', and its situation is explained in Plate LX XVII. It will be seen from that Plate, that ix large binn is situated over the mash tuns. This receives the grist as fast as it is ground. and here it is resened till wanted. It is the opinion of some brewers, that the malt, when ground, is the better of being kept some days before it is mashed; but we do not know any reason for this If this has any effect, it can only arise from exposure to the air; though it cannot have much of this in the close binn over the mash tun, to which it is conveyed by the screw, which is also in closed in a tight trough, that the fine flour, which will unavoidably be produced in the grinding, may not be lost, as is the case in works where this is not attended to. When the grist is Jet down .nto the tun, it is en closed by sackcloth, hooked round the edge of the tun, and round the lower edge of the binn, by which means none of the flour is lost in dust in any part of the pro cess.
Besides the mashing engine which we have describ ed, many others of different constructions are in use. One of these invented by Mr Goodwynne, and employ ed by him in his extensive brewery, is deserving of no tice. It is of the figure of a half cylinder, with the cen tral line placed horizontal. In this central line, an iron shaft is fitted, and turned round by wheelwork from the steam engine. It has several iron arms fixed perpen dicularly upon it at different parts of its length, which, as the shaft revolves, sweep the whole contents of the tun ; and having teeth fixed in them, they effectually mash up every part of the goods. These arms are not all fixed on the same side of the axis, but arc arranged at equal angles round it, so as to dip into the goods in succession. When, by their continual motion, the is accumulated at one side of the tun, the motion of the shaft is reversed by wheelwork adapted for the purpose, and this brings the grist back again.
Another machine, which we have seen at Messrs Clows and Co. was contrived by Mr. Silvester. It consists of a vertical spindle in the c....ure of the mash tun ; and upon this, an iron arm of a length sufficient to extend across the diameter of the am, slides up and down, through the depth of the grist. The arm is provided with teeth projecting from one side of it, like a rake ; and these teeth are so contrived, that when the arm de scends, they hang down vertical, and their points pene trate the goods, without disturbing them; but when the arm reaches the bottom of the tun, the teeth are turned by the machine, so as to be horizontal, and are then drawn up ; during which action they raise a portion of the grist, from the bottom to the top. The next time
the arm descends, it is turned round with its spindle a few degrees, so as to take a fresh portion of the tun ; and in this manner its action continues, till in about 30 or 40 strokes it completes its revolution round the tun. This construction admits of the mash tun being cover ed close over by large doors, a circumstance of great importance for retaining the heat.
It will be proper to notice here a proposal by Dr Shannon, for a mash tun, which is recommended to be made air tight, and inclosed within another vessel also air tight ; the space between them to be filled with steam supplied from the steam engine, or from a boiler made on purpose. This method of keeping up the heat would undoubtedly be attended with great advantages, but some difficulties would occur in the execution of it. Setting aside the enormous expense of two such ves sels, it is essential in a mash tun that the malt, after be ing mashed, can be quickly removed from it, and that when empty the air should have free access to every part of the tun, that it may dry without becoming musty.
A patent for the same purpose was obtained by Mr Long in 1790. Ile proposes the mash tun to be con structed as usual, but with a small boiler for water by the side of it. From this boiler a pipe proceeds, and entering the .tun near its bottom, makes one or two revolutions within it, and communicates the heat of the water which it contains to the goods in the tun. It then passes out again near where it first entered, and delivers the water into a cistern, from which it is pumped up to the copper, and the place again heated. By this cir culation of hot water through the tun, the heat, during the mashing, may be regulated as the brewer thinks most proper. The patentee advises, that the liquor should be first let upon the malt from 20 to 30 degrees lower than usual, and that the wort should be afterwards brought to the proper heat by the small boiler. The same effect may be produced by a small fire-place under the mash tun. We have little doubt but this practice would be attended with sonic advantages in making a proper extract, and would totally remove the effect of the weather upon the process of mashing.
The next utensil which we have to describe, is the brewing copper. This machine was formerly only an open copper, set in brickwork over a fire place, in the same manner as the boilers which arc used for culinary purposes ; but in the immense coppers which are now employed, the saving of fuel is an object of great im and every means which can tend to this are adopted.