Like the Atlantic between the Old and the New Worlds, its waves wash the shores of the two worlds of matter and of mind; its tributary streams flow from both; through its waters, as yet unfurrowed by the keel of any Columbus, lies the road, if such there be, from the one to the other; far away from that North-West Passage of mere speculation in which so many brave souls have been helplessly frozen up.

Such was the spirit in which, after his long day’s work, he added to his labours in physical science a search in another, and to his notion a cognate province of thought and speculation.  Many a sleepless night in these years the candle was lighted beside his bed, and for a couple of hours after midnight he would devour works on philosophy—­English, German, and French, and occasionally Latin.  To a mind at once constructive and intensely critical of unsound construction he added a quality possessed by few professed philosophers—­a large knowledge of the workings of life, of the human thinking machine, in addition to various other branches of physical science.  As he put it, the laboratory is the forecourt to the temple of philosophy.  For the method of the laboratory is but the strict application of the one sound and fruitful mode of reasoning—­the method of verification by experiment.  Evidence must be tested before being trusted.  The first duty of such a method is to question in order to find good reason; Goethe’s “taetige Skepsis,” a scepticism or questioning which seeks to overcome itself by finding good standing-ground beyond.  Authority as such is nothing till verified anew.  The creeds of ancient sages, the dogmas of more modern date, must equally bear the light of widening knowledge and the tests that prove the gold or clay of their foundations, the stability of the successive steps by which they proceed.

In all this reading Huxley found nothing to shake what he had learnt long before from Hamilton—­the limits set to human knowledge and the impossibility of attaining to the ultimate reality behind the phenomena presented to our cognition.  The problems of philosophy, set forth with unsurpassed clearness for all who will read in our great English writers, were not solved by soaring into intellectual mists.  To those who declared they had attained this ultimate knowledge by their own inner light or through an alleged revelation in historical experience, the question remained to be put:  How do you verify your assertion?  Is the historical evidence on which you build trustworthy?  And if in certain departments this evidence is clearly untenable, what guarantee have you that in other departments evidence of similar character is tenable?  The fine-spun abstractions of the Platonists and their kin, unchecked by a natural science which had not yet the appliances necessary for its growth; the orthodoxies of the various churches, so singularly differentiated in the course of development from the simplicity of