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THE POPULAR SCIENCE MONTHLY. 



earrying on various industries and arts, there 

 are now but scattered tribes of savages. Un- 

 questionably causes like those which pro- 

 duced these retrogressions, have been at 

 work during the whole period of human ex- 

 istence. Always there have been eosmical 

 and terrestrial changes going on t which, 

 bettering some habitats, have made others 

 worse ; always there have been over-popula- 

 tions, sp readings of tribes, and escape of the 

 defeated into localities unfit for such ad- 

 vanced social life as they had reached; al- 

 ways, where evolution has been uninter- 

 fered with externally, there have been those 

 decays and dissolutions which complete the 

 cycles of soeial changes. That supplanting 

 of race by race, and tlirusting 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 be- 

 gins 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 phil- 

 osophic shaking-up as the Belfast Ad- 

 dress 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 ingen- 

 iously 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 scien- 

 tists he says : " Why not go on observ- 

 ing, 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 pictur- 

 ing power of the mind, they must re- 

 linquish the claims of positive science." 

 This strikes us as a quite erroneous 

 view of the case. The scientific investi- 

 gator can no more renounce the pictur- 

 ing 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 opera- 

 tions, and, in fact, put an end to thought 

 itself. For what is thought but repre- 

 sentation in consciousness, and what is 

 it to represent but to reproduce men- 

 tally, to picture, to image, or exercise 

 the image-forming faculty the imagi- 

 nation? There are, of course, other 

 mental operations, but they are per- 

 formed upon the representations in con- 

 sciousness upon the objects of thought 

 imagined, or imaged to the mind's eye. 

 Not a step can be taken in science ex- 

 cept 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 



