Writings of Spencer embody the spirit of Descartes in the knowledge of our own day, and may be regarded as the Principes de la philosophic of the 19th century; while, whatever hesitation may not unfrequently be felt by less daring minds in following Haeckel in many of his speculations, his attempt to systematize the doctrine of evolution and to exhibit its influence as the central thought of modern biology, cannot fail to have a far-reaching influence on the progress of science.
The Bengal tiger is not unfrequently met with, and wild boars are abundant.
The liberty of the press not unfrequently degenerated into licence, and sane liberalism was often replaced by socialistic dreaming.
When a religion begins to ossify into a system of formulas and observances, those who protest in the name of heart-religion are not unfrequently known by the name of mystics.
In particular, the Roman "North Road" which ran from York through Corbridge and over Cheviot to Newstead near Melrose, and thence to the Wall of Pius, and which has largely been in use ever since Roman times, is now not unfrequently called Watling Street, though there is no old authority for it and throughout the middle ages the section of the road between the Tyne and the Forth was called Dere Street.