The exact form of these three interior valleys, which had an important influence on the construction and history of the city, is still imperfectly known, as they are to a great extent obliterated by vast accumulations of rubbish, which has filled them up in some places to a depth of more than 100 ft.
Granted that, ideally, scientific knowledge ought to be able to demonstrate all truth, is it safe, or humane, for a being who is imperfectly started in the process of knowledge to fling away with scorn those unanalysed promptings and misgivings " Which, be they what they may, Are yet the fountain light of all our day, Are yet a master light of all our seeing.
At that date the science of chemistry was very imperfectly known, and the real constituents of ordinary remedies so little understood that different virtues were attributed to different products containing the same constituents.
Even here, however, general agreement has not ~en reached; and the questions involved in relating the facts the distribution of plant communities to the factors of the tbitat are very imperfectly understood.
Woody or lignified cell-walls appear to contain substances called conifer-in and vanillin, in addition to various other compounds which are imperfectly known.