I’ve been browsing a few old books online, and came across a couple of nice quotes on Port and Portuguese wines from a late 19th Century text:

‘The mode of making port wine is extremely unclean, and the proceedings are very crude and elementary; nevertheless, so good a product is obtained that its faults are, as it were, drowned in its good qualities. The great object of the wine makers must be to produce good and durable wine with only so much alcohol as shall not be injurious to the wine drinker. This cannot be said to be the case with the ordinary thick, heavy, so-called loaded ports of 40 to 42 of proof spirit, and for this reason whole classes of society in Britain have ceased to drink any port wine whatever. Yet good port wine is one of the most wonderful productions of the earth ; and I am sure, when vinification in all its branches and variations shall be once fully understood on the Alto Douro, it will produce such excellent red wines as hitherto have not been exported from the Peninsula.’

‘Portugal in itself, poor, yet climatically highly endowed, is capable of producing a variety of the most beautiful grapes, and a variety of wines, which, if properly made, would not be surpassed by those of any other country. The people are good-natured, industrious, and hard-working, and they have what is very agreeable to a person who comes from this country, a great regard for an Englishman. If these good people would continue to plant their vineyards with particular sorts of grapes, such as have been proved in the great Alto Douro districts, in Bucellas, or Collares, to be so excellent;if they were to abandon that horrid practice of making sweet and cooked wines; if they were to study the conditions by means of which they might avoid the natural climatic difficulties which produce fungi and acidity; if they introduced more cleanliness into their sheds, and if they were to have their cellars underground; if they were to avoid large tonels and adopt small casks, I have no doubt Portugal, one of the most essential English vineyards, would produce other wines besides port, which would be of the greatest use hygienically and socially to this country. We have a great trade with Portugal in other respects, taking there our manufactures, and bringing away in return large quantities of produce, cattle, grapes, figs, apples, and a variety of other articles too numerous to mention; and an improved quality of wine would find in this country a very ready and grateful market.’

From: A TREATISE ON WINES: THEIR ORIGIN NATURE AND VARIETIES WITH PRACTICAL DIRECTIONS FOR VITICULTURE AND VINIFICATION
By J. L. W. Thudichum
London, George Bell & Sons 1893