carrying on various industries and arts, there are now but scattered tribes of savages. Unquestionably causes like those which produced these retrogressions, have been at work during the whole period of human existence. Always there have been cosmical and terrestrial changes going on t which, bettering some habitats, have made others worse; always there have been over-populations, sp readings of tribes, and escape of the defeated into localities unfit for such advanced social life as they had reached; always, where evolution has been uninterfered with externally, there have been those decays and dissolutions which complete the cycles of social changes. That supplanting of race by race, and thrusting into corners such inferior races as are not exterminated, which are now going on so actively, and which have been going on from the earliest recorded times, must have been ever going on. And the implication is that remnants of inferior races, taking refuge in inclement, barren, or otherwise unfit regions, have retrograded."
MENTAL PICTURING IN SCIENCE.
We pointed out some indications last month of the mitigated asperities in the Tyndall controversy, as evinced by the tone of the graver periodicals, and may now observe that a much more conciliatory and reasonable spirit begins to be manifested by the newspaper press. The topic is by no means worn out, and if our theological friends have the interests of education at heart, and are at all capable of gratitude, they will vote a medal of honor to Prof. Tyndall for his eminent services in arousing multitudes to think carefully upon important questions of which they have hitherto thought carelessly or not at all. There has not, in a long time, been such a general scientific and philosophic shaking-up as the Belfast Address has produced; and the result must be, that many will work their way to much clearer conceptions of the scope of science and its relations to religion.
A leading article appeared in the last issue of Church and State, in the most excellent temper, but still ingeniously protesting against some of Prof. Tyndall's views. In his late reply to his critics, the professor has said: "The kingdom of science, then, cometh not by observation and experiment alone, but is completed by fixing the roots of observation and experiment in a region inaccessible to both, and in dealing with which we are forced to fall back upon the picturing power of the mind." To this the writer takes exception, and questions whether it is right or advisable for the scientist "to fall back on the picturing power of the mind." He thinks it is allowable for the theologian to do this, but to scientists he says: "Why not go on observing, and leave others to conjecturing?" And, again, he remarks: "Of one thing we are sure, that, so far as the scientific investigators fall back upon the picturing power of the mind, they must relinquish the claims of positive science."
This strikes us as a quite erroneous view of the case. The scientific investigator can no more renounce the picturing faculty in his mind, than he can renounce the heart in his body; and he can no more confine himself to observing and leave conjecturing to others, than he can confine himself to digestion and leave respiration to others. To suppress the picturing power of the mind would put an embargo on all intellectual operations, and, in fact, put an end to thought itself. For what is thought but representation in consciousness, and what is it to represent but to reproduce mentally, to picture, to image, or exercise the image-forming faculty—the imagination? There are, of course, other mental operations, but they are performed upon the representations in consciousness—upon the objects of thought imagined, or imaged to the mind's eye. Not a step can be taken in science except by this mental procedure. The object of science is truth, and what is truth but the faithful representation in thought of the order and relations of natural things? Everybody imagines, but their mental images do not always
