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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



have reached its perhaps unattainable goal only 

 when it has succeeded in combining the multi- 

 tude of its conceptions in a comprehensible scheme 

 of the universe. We must not, however, forget 

 that even then only one chapter of the great book 

 of Nature would have been made out ; we should 

 still have to give ourselves an account of the past 

 and future history of the Cosmos. 



If truth in this sense is to be denned as the 

 agreement of our ideas with the things they rep- 

 resent, then the discovery of truth would appear 

 to be a process of thought in which the members 

 of the subjective series are connected together in 

 a manner answering to the connection between 

 the members of the objective series. The sub- 

 jective association must conform to the objective. 



To this synthesis do all those great hypothe- 

 ses owe their origin which have mace their mark 

 in the history of the human mind. 



The greater the abundance of the empirical 

 material developed by research, the easier it is to 

 make this synthesis. Nevertheless, great dis- 

 coveries do not by any means always coincide 

 with periods of active and fruitful research, nor 

 is Zimmermann's saying always true, that " the 

 more the eyes have seen, the more does the mind 

 see too." Indeed, it very often happens that in 

 such periods we cannot see the forest, for the 

 trees ; while in other periods genius anticipates, 

 using a relatively small sum of empiric data with 

 the utmost economy, on them basing hypotheses 

 which later, when the sum of confirmatory phe- 

 nomena has been much increased, find universal 

 acceptance. Such efforts as these at syntheti- 

 cally combining individual phenomena whose 

 relations are not yet ascertained, and from the 

 aggregate of the phenomena constructing the or- 

 ganism, so to speak, of the universe, thus ren- 

 dering it intelligible, might be compared to the 

 task of reconstructing, out of some disconnected 

 words that still remain, the text of a badly-muti- 

 lated document. 



No essay of this kind is so well calculated to 

 excite our admiration as that of Kant in con- 

 structing, out of the at best extremely scanty 

 materials at his command, the history of that 

 little cosmical island which we call the solar sys- 

 tem. 



For what did Kant know of that system ? If 

 we leave out of view the comets, which he did 

 not take into account, Kant was acquainted with 

 six principal planets and nine moons : he knew 

 that these bodies revolve round the sun, in one 

 and the same direction ; that Saturn has rings ; 

 that the orbits of the planets are approximately 



circular, and that their orbital planes nearly co- 

 incide. 



What do we know of the same subject? Not 

 only has the number of the planets (the asteroids 

 included) increased to one hundred and sixty- 

 four since Kant's time, that of the moons has 

 increased to eighteen, and all these bodies give 

 confirmation to the nebular hypothesis. Further, 

 we are acquainted with Plateau's interesting ex- 

 periment in which he imitated in miniature the 

 genesis of the solar system by causing a sphere 

 of olive-oil to rotate in a mixture of water and 

 spirits of wine, and thus from the standpoint of 

 the universality of terrestrial laws demonstrated 

 the correctness of the Kantian hypothesis. 

 Again, we know of the existence of cosmic neb- 

 ulae — the primordial matter inferred by Kant — 

 the gaseous constitution of which is demon- 

 strated by the spectroscope : nay, even the 

 telescope enables us to descry gaseous rings, 

 analogous to the rings of Saturn, encircling 

 the cosmic nebulae. Finally, a number of vari- 

 able and of new stars have been discovered. All 

 of these bodies are, as it were, words that were 

 altogether wanting in the text examined by Kant, 

 but which can be of very great service to us in 

 writing the history of the Cosmos : hence, it is 

 no wonder if in the nebular hypothesis we recog- 

 nize a degree of probability very closely border- 

 ing on certitude. But it is a thing worthy of all 

 admiration that in the mind of the philosopher 

 of Kbnigsberg there should have been formed a 

 train of ideas whose agreement with a train of 

 long-past phenomena could at the time be de- 

 monstrated only at a few points, but into which 

 all the discoveries since made fit with perfect 

 ease, like the links of a chain. 



Kant was very far from believing that by this 

 hypothesis he had done away with the need of 

 further research ; but it almost looks as though 

 we, in our zeal to add to the material confirma- 

 tory of the nebular hypothesis, had forgotten to 

 note the gaps in it that no discovery can fill, and 

 the defects under which it still indisputably 

 labors. And yet in the materials accessible to 

 Kant there is to be found, as we shall see, that 

 which should incite us to a reconstruction of the 

 hypothesis. We are collecting building stones, 

 without reflecting that, in proportion as materials 

 accumulate, the edifice should rise. We make 

 that an end which is but a means ; but, since in 

 the Cosmos all phenomena are systematically con- 

 nected with one another, it cannot be our task 

 simply to accumulate them in our minds in dis- 

 connected shape : on the contrary, in our mental 



