"Ale. A well-known amber-coloured fermented liquor of considerable strength, but varying in the amount of alcohol which it contains, according to the option of the particular ale brewer. Edinburgh ale contains apparently more saccharine matter unfermented than other ales, and is strong. Burton ale has more hops added, and is hence termed pale bitter ale. The Scotch ale is said to be brewed during the cold months of the year, only one mash of half-an-hour's duration being made, and the heat of the liquor raised to 180°; it is then drained off into the wort copper. The malt is then deprived of all its soluble matter by sparging, or dashing over hot water of 180° for eight or ten times successively, the liquor draining through by apertures placed at the sides of the mash tun, and armed with stopcocks. One gallon of yeast is added to 240 gallons of wort, and the fermentation begun at 50°, and continued for two or three weeks: four lbs. of hops are used to the quarter of malt. The following table by my pupil, Mr. John Wright Currie, of the Perth Brewery, gives the strength of various ales brewed in that establishment. The experiments were made with great care in my laboratory.
Scottish Ales.
Absol. Alcohol per cent. Extract per cent. Water per cent. Export Ale 7.96 3.75 88.29 India Ale 8.97 2.75 89.28 No. 3 Ale 7.055 5.7 87.25 No. 4 Ale 7.855 6.675 85.47
Scottish Ale Brewing.—To brew 20 barrels of ale, 80 bushels of malt and 80 lbs. of hops are required Three or four barrels of water at 180º are let down into the mash tun, and at the same time the sluice of the malt bung is opened, and the malt and remainder of the liquor at 175° run down together, and stirred. The mashing requires three hours, when the sparger (sprinkler) is fixed to the head of the tun. The sparger is a copper cylinder five or six inches in diameter, closed at both ends, and nearly so to within a foot of the centre, which is open, with a cross division against which a run of liquor by a spout from the copper strikes and sends it round the. tun. An iron bar is fixed across the latter, on which the sparger is placed on a pivot. Its two arms extend the width of the tun, the inferior side of these being pierced with small holes similar to the mouth of a watering-pan, from which as it revolves, the liquor escapes and sprinkles the mash. The water in the boiler being tempered to the heat required for sparging, (185°,) the taps of the mash tun are slacked, and the worts permitted to flow out slowly, the sparger being set in motion—this operation being merely a continuation of the mashing. I may add, that having examined most of the waters used by the Edinburgh ale brewers, I have found them all very hard waters, containing a large quantity of carbonate of lime. If any virtue is to be attributed to the water, it may be presumed that the carbonate may act by neutralizing any acid as soon as it is formed. The 30 barrels of wort, 72 lbs. saccharine extract per barrel, are boiled for half-an-hour, and 40 lbs. hops added; another half-hour's boiling takes place, the remaining hops are added, and the wort boiled for another half-hour. Worts of the gravity of 50 lbs. extract per barrel strengthen 5 lbs. per barrel in one hour's boiling, and worts of 100 lbs. in one and a halfhour strengthen 15 lbs. So that the brewer can easily judge of the amount of boiling required by the use of the saccharometer. The worts, after a quarter of an hour, are run into the hop back, and then spread on the coolers, where they remain twelve hours; during this time they lose one-eighth of their bulk by evaporation. The worts being cooled to 53°, one barrel of wort is run into the gyle, and 6 gallons of yeast added, and thoroughly mixed; the remaining wort is then added. In Scotland, the temperature for commencing the fermentation is about 52.5°, in England 62.5°. In twenty-four hours the first stage ends, the surface being characterized on the edges by a white circle, and irregular patches of white breaking through, and soon being covered with froth. The head of froth is beat down, and the process continued for twenty-four hours more. In eight days the heat has increased 10°. The brewer judges of the period to stop the fermentation by the saccharometer, which indicates the amount of sugar which has been converted into alcohol. The next process is cleansing. In Edinburgh the ale is run finished from the gyle into the casks in which it is sold. In Alloa and Stirling it is run into butts, from which it is rocked into casks, a pint of fillings or prepared wort being put at the same time into each."
"Dictionary of chemistry with its applications to mineralogy, physiology and the arts" by Robert Dundas Thomson, 1870, pages 26 - 27.
In the first paragraph it sounds like he's confusing Burton Ale and Burton Pale Ale. It's a mistake many have made. I'm not convinced by that description of Scottish mashing, either.