"Now beer can be made to vary greatly in its quality according to the way in which this process of brewing has been carried on. Of course, the stronger the wort the more sugar, and the more alcohol as the result of fermentation. But you may carry the fermentation up to various points. You may make, at first, a sweet beer or ale by stopping the fermentation, but which eventually shall become very strong by age and fermentation. Such are our sweet ales, and ales that get strong by keeping. By carrying on the fermentation you may exhaust all the sugar, and by using malt free from gum you get a clear pale ale, and by adding a larger quantity of hops, our pale bitter ales are produced. The fermentation of these ales being over, they can be sent to a distance: hence the practice of sending such ale to India. They are, however, generally strong ales, on account of the completeness of their fermentation, and are objectionable on that account. I find that our ordinary bottled pale ale contains more alcohol than hock, claret, or Moselle wines, and as much as Burgundy.
The brewing of the pale and bitter ales for the Indian market has led to a great change in public taste for beer, and milder pale and bitter ales are extensively brewed for domestic consumption. My own conviction is, that an immense benefit has accrued from this, as the strong and sweet ales formerly drunk were objectionable on many accounts. In the first place, they caused a greater consumption of alcohol than was beneficial; and in the next place, the sugar became a source of disorder and disagreement in the stomach. The increased quantity of hop also secures in the mild bitter ales a tonic effect which is very beneficial. For habitual consumption in families the mild bitter ale, with not more than half an ounce of alcohol in the pint, is to be commended above all others.
London porter, of which prodigious quantities are consumed daily in this metropolis, is coloured with the black malt. It contains about three quarters of an ounce of alcohol in the pint, and more sugar and less hops than the pale ales. It is, however, miserably drugged in the public-houses. Its strength is reduced by water, and its qualities are brought up again by treacle, liquorice, and salt, and various narcotic agents are added to make up for the loss of alcohol. To such a condition has the porter-drinking population been brought that they do not know genuine porter when they drink it, and having acquired a taste for this wretched substitute, they reject the unadultereated article.
Stout is only a stronger form of porter. Good draught stout contains about one ounce and a half of alcohol in the pint.
All beers, ales and porters may be bottled; and this is done before the active fermentation is over, so that this process engenders in the bottles liquid a quality of carbonic acid gas, which converts the stouts and porters which contain a great quantity of gum into one mass of froth. It is not so common in pale ale, but here it is not uncommon to lose half the ale by its seething over the glass when poured from the bottle.
Bottled ales are generally stronger than those on draught; and with some persons the frothing state of the beer seems to agree better than the less lively condition of that from the cask. It is the same with wines and water; and carbonated waters and effervescing wines have the same recommendation.
I have not time to dwell on the varieties of beers, ales and porters sold in this country. But they differ very much; and the impossibility of brewing the same beer in two different districts is an interesting fact. One of the most remarkable facts of this sort is the generally acknowledged excellence of the Burton beers. Now it appears there is only one condition at Burton that causes its beer to differ from all others, and that is, the presence in the water of a certain quantity of sulphate of lime. My friend, Dr. Letheby, has pointed out that this is the real cause of the success of the pale ale breweries of Burton. He says, such water will not extract the saccharine and albuminous matters of malt so fully as others, and that this is desirable in the manufacture of pale ales. I would, however, bear my testimony to the great intelligence and care with which the great pale ale breweries are conducted at Burton-on-Trent. Such prevision and intelligence brought to bear on the minutest details of a great manufactory, cannot fail to be productive of the best results."
"On food" by Edwin Lankester, 1864, pages 221 - 224
The author splits Pale Ales into two groups: the strong type and the light type. The strength of the former is "on account of the completeness of their fermentation". Or the very high degree of attenuation. We've seen Bass and Allsopp Pale Ales that were 85% to 90% attenuated. Their gravities weren't necessarily that high - mostly 1060 to 1070 - but the very high attenuation left some over 7% ABV.