Auc. 8, 1884.] 



♦ KNOWLEDGE ♦ 



113 



pected manner the age of antiquity, " Know thyself." For 

 he has begun to perceive a strong probaliility, if not an 

 actual certainty, that his own living nature is identical in 

 kind with the nature of all other life, and that even the 

 most amazing side of that nature — nay, the most amazing 

 of all things within the reach of his knowledge — the human 

 mind itself, is but the topmost inflorescence of one mighty 

 growth, whose roots and stem and many branches are sunk 

 in the abyss of planetary time. 



The problem, therefore, which in this generation has now, 

 for the first time, been presented to human thought, is the 

 problem of how this thought itself has come to be. A 

 question of the deepest importance to every system of 

 philosophy has been raised by the study of biology, and it 

 is the question whether the mind of man is essentially the 

 same as the mind of the lower animals, or, having had, 

 either wholl)- or in part, some other mode of origin, is 

 essentially distinct, differing not only in degree, but in kind, 

 from all other types of physical existence. 



First, then, let us consider the question on purely '> frim-i 

 ground. The process of organic and of mental evolution has 

 been assumed to be continuous throughout the whole region 

 of life and of mind, with the one exception of the mind of 

 man. On grounds of a very large analogy, therefore, we 

 should deem it antecedently improbable that the process of 

 evolution, elsewhere so uniform and ubiquitous, should be 

 interrupted at its terminal phase ; and I think that, looking 

 to the very large extent of the analogy, this antecedent 

 presumption is really so considerable that it could only be 

 fairly counterbalanced by some very cogent and unmis- 

 takable facts, showing a ditference between animal and 

 human psychology so distinctive as to render it in the 

 nature of the case virtually impossible that one could ever 

 have graduated into the other. This I posit as the first 

 consideration. 



Next, still restricting ourselves to the <> priori aspect of 

 the matter, it is unquestionable that human psychology in 

 the case of every individual human being presents to actual 

 observation a process of gradual development, or evolution, 

 extending from infancy to manhood ; and that in this pro 

 cess, which begins at a zero level of mental life and may 

 culminate in genius, there is nowhere and never observable 

 a sudden leap of progress, such as the passage of one order 

 of psychical being into another distinct in kind might 

 reasonably be expected to show. Therefore, it is a matter 

 of observable fact that, whether or not human intelligence 

 differs from animal in kind, it certainly admits of gradual 

 development from a zero level ; and to this we must add 

 that, so long as it is passing through the lower phases of 

 that development, it assuredly ascends through a scale of 

 mental faculties which are pari passu identical with those 

 that are permanently presented by the psychological species 

 of the animal kingdom. These facts, which I present as a 

 second consideration, tend still further, and I think most 

 strongly, to increase the force of the antecedent presumption 

 against the process of evolution having been discontinuous 

 in the region of mind. 



Again, it is likewise a matter of actual observation, that 

 in the history of our race, as recorded in documents, tra- 

 ditions, antiquarian remains, and flint implements, the 

 intelligence of the race has been subject to a steady process 

 of gradual development — a general fact which admits of 

 any amount of special corroboration by comparing the 

 psychology of existing savages, where the process of evolu- 

 tion in the past has not been so rapid or has in part been 

 arrested, with that of civilised man. This is the last 

 consJderation that I shall adduce of the cl priori kind, and 

 its force consists in the fact of its proving that if the 

 process of mental evolution was interrupted between the 



anthropoid apes and primitive man, it must again have 

 recommenced with primitive man, and since then have 

 continued as uninterruptedly in the human species as it 

 previously did in the animal species. This, to say the 

 least, upon the face of the indisputable facts, or from a 

 merely antecedent point of view, appears to me a highly 

 improbable supposition. At all events, it certainly is not 

 the kind of supposition which men of science are disposed 

 to regard with favour elsewhere : for a long and arduous 

 experience has taught men of science that the most helpful 

 kind of supposition which they can bring with them into 

 their investigations of nature is that kind of supposition 

 which recognizes in nature the principle of continuity. 



Taking, then, all these <> priori considerations together, 

 they must, in my opinion, be fairly held to make out a 

 very strong prima facie case in favour of the view that 

 there has been no interruption of the developmental process 

 in the curse of psychological history, but that the mind of 

 man, like the mind of animals — and, indeed, like everything 

 else in organic nature — has been evolved. For these con- 

 siderations show, not only that on analogical grounds any 

 SMch interruption must be held as in itself improbable ; but, 

 also, that the human mind unquestionably admits of 

 having been slowly evolved from the zero level, seeing that 

 in every individual case, and during many past millenniums 

 in the history of our species, the human mind actually does 

 and has undergone the process in question. 



In order to overthrow so immense a presumption as is 

 thus erected on a priori grounds, the psychologist must 

 fairly be called upon to supply some very powerful con- 

 siderations of an a posteriori kind, tending to show that 

 there is something in the constitution of the human mind 

 which renders it impossible, or, at all events, exceedingly 

 difficult, to imagine that it can have a genetic relation to 

 mind of lower orders. 



NATURAL GAS FUEL AT PITTSBUEG. 



AT the recent meeting of the American Society of Me- 

 chanical Engineers at Pittsburg, the report of the 

 committee appointed to investigate the whole subject of 

 natural gas was made, and many interesting particulars, 

 we read, were given. 



Though Pittsburg is within reach of three or four prolific 

 localities, and gas has been used for many years, it is but 

 recently that any organised eflbrt has been made to use it 

 on a large scale. Already there are 1-30 companies 

 charteredin the State, representing over -2,000,000 dols. ,; 

 and gas is brought from eight to twenty-five miles for use 

 in the city. Five-inch mains are being followed by 8-inch, 

 new wells are being bored, and the time when Pittsburg 

 shall become a smokeless city may not be far distant. 

 Though the gas is used under a pressure of a few ounces, 

 the pressures at the wells run from 50 to 12-5 pounds; 

 this is due to the friction in the mains, five pounds being 

 allowed for each mile. If the flow be shut olT the pressure 

 runs up much higher, and great difficulty has been ex- 

 perienced in making tight joints ; cast iron is too porous, 

 and ordinary pipe-threads do not fit well enough. A 

 number of new coupling devices were exhibited, in some of 

 which a lead packing was used. No allowance for expan- 

 sion need be made, as the gas maintains an even tempera- 

 ture of about 45- Fah. \Yhen gas is allowed to burn freely 

 at the mouth of a well, the cold produced by the expansion 

 is such that ice has been projected through the flames. 



The gas is used in all kinds of furnaces for making steam 

 iron, glass, &c. ; and electric light carbons, and the finest 



