It is very odd, perhaps, in Edmund Burke's "On the Sublime and Beautiful" to read
On the whole, the qualities of beauty, as they are merely sensible qualities, are the following: First, to be comparatively small. Secondly, to be smooth. Thirdly, to have a variety in the direction of the parts; but, fourthly, to have those parts not angular, but melted, as it were, into each other. Fifthly, to be of a delicate frame, without any remarkable appearance of strength. Sixthly, to have its colors clear and bright, but not very strong and glaring. Seventhly, or if it should have any glaring color, to have it diversified with others. These are, I believe, the properties on which beauty depends; properties that operate by nature, and are less liable to be altered by caprice, or confounded by a diversity of tastes, than any other.
Then, this reflections the older distinction between the sublime and the beautiful:
On closing this general view of beauty, it naturally occurs that we should compare it with the sublime; and in this comparison there appears a remarkable contrast. For sublime objects are vast in their dimensions, beautiful ones comparatively small; beauty should be smooth and polished; the great, rugged and negligent: beauty should shun the right line, yet deviate from it insensibly; the great in many cases loves the right line; and when it deviates, it often makes a strong deviation: beauty should not be obscure; the great ought to be dark and gloomy: beauty should be light and delicate; the great ought to be solid, and even massive.
And then there's the picturesque, that which is not beautiful in itself but would make a beautiful thing more attractive in a painting. . . such as some roughness breaking in that smoothness.
None of which is really difficult to understand once explained. In Paris To the Moon, the author had told his son about the difference between the sublime and the beautiful and the boy was able to exemplify it: the T. rex skeleton was sublime, and a little girl, a pre-school schoolmate of his, was beautiful.
The case is when the characters take it for granted that no one would consider Niagara Falls to be beautiful. Or when taking a boat along a river, there may be sublime wild views, and picturesque wild views, but a beautiful view is, by definition, cultivated land. (Early tourists prefered the Hudson and the Connecticut to any other rivers in the United States, because they were the most cultivated banks.)