; Vol. XXm. No. 4.] 



POPULAR SCTE1\"CE KEWS. 



51 



folded into tlie latter, which then serves as a sheath, 

 allowing the whole to be carried without danger to 

 the person. 



Thus we see that the history of the class of things 

 to which the pocket-knife belongs, has been one of 

 progressive development. In other words, the 

 pocket-knife, and everv other form of cutting-instru- 

 ment, has come to be as it now is by a jirocess of 

 evolution from the primitive cutting-instrument. It 

 is as if the chipped stone axe of primitive man was 

 the ancestral form from which have descended every 

 kind of bladed instrument now- in use. Given the 

 original edged implement, it needed only successive 

 slight modifications, proceeding in varying direc- 

 tions, to give rise to every form of cutting-instru- 

 ment of to-day. If we had all the materials of tliis 

 history — if we had specimens of all the forms of 

 edged instruments that have ever been made — we 

 could arrange them in such order as to show their 

 derivational relations, and we should see that every 

 kind of instrument now in use stands at the end of 

 a series, and that the lines marking these series run 

 backward, uniting and converging, and finally ter- 

 minate in the original cutting-instrument — the 

 chipped flint-stone. 



It is to such a process, tHtn, as that by which the 

 axe of chipped stone became the pocket-knife of to- 

 day, that the name evolution is given. It is desira- 

 ble for us to apprehend clearly not only the fact of 

 the process, but also the causes determining and 

 regulating it. For, in regard to evolution as a 

 doctrine of science, it is to the causes and laws of 

 the process that the whole controversy relates. If, 

 therefore, we can understand thsse aspects of the 

 subject in respect to the evolution of the minor 

 article of handicraft whose history we have traced, 

 we shall be better prepared to consider the same 

 questions in respect to evolution in the realm of 

 nature. We may place the results of our present 

 study under two or three heads, as follows : 



1. It was a process of formation , not of origina- 

 tion. Evolution explains how the knife, as a species 

 of cutting-instrument, came to have its peculiar 

 form, but it does not explain how there came to be a 

 cutting-instrument in the first instance. In other 

 words, it does not account for the origin of cutting- 

 instruments, but, the original being given, it 

 accounts for the various forms that succeeded it. 

 The class had its origin in the idea of primitive 

 man ol utilizing a sharp stone for cutting purposes. 

 It is this idea that explains the existence of the 

 pocket-knife: evolution explains its form. It is true 

 that the ou<se of the evolution was of the same na- 

 ture as the cause of the origination. It was human 

 ideas that caused the successive modifications (evo- 

 lution) of the original cutting-instrument, just as it 

 was a human idea that causef^ it to be a cutting- 

 instrument at all (origination.) Nevertheless, we 

 are to distinguish sharply between the two: origi- 

 nation relates to the calling into being of a thing; 

 evolution to the successive modifications of a thing 

 already existing. Nothing can be created, in the 

 absolute sense, by a process of evolution. 



2. The successive modifications, or steps of forma- 

 tion, were in adaptation to circumstances. The 

 chipped stoTie implement was succeeded by a pol- 

 ished one, because the successors of primal man, 

 more intelligent than he, had larger uses for an axe, 

 and felt the need of one with smooth surfaces. Thus 

 the first step in the process of evolution was in 

 adaptation to a change of circumstances. It was so 

 with each subsequent step. With expanding intel- 

 ligence, with increasingly complex ways of living, 

 there were more and more varied uses for edged 

 implements, and in each succeeding period they 

 were modified in adaptation to the needs of the 

 time. We shall not err if we deduce, as a general 



principle of evolution, that changes of form always 

 take place in adaptation to the conditions then ex- 

 isting. 



3. The steps of formation were progressive and 

 diverging. Upon the whole, each new sort of cut- 

 ting-instrument was an advancement upon those 

 that preceded. The tools made of bronze were bet- 

 ter than those made of stone, and the iron tools were 

 superior to both. But there was not only improve- 

 ment in the quality of the material, but also in the 

 character of the workmanship, and, more especially, 

 in the plan of the tool — its adaptation to the pur- 

 pose for which it was used. The axe with a handle 

 was greatly superior to any previous form without 

 handle. Moreover, the axe with handle was the 

 prototype of every subsequent form of handle-and- 

 blade instruments 'Once the advantage of a handle 

 to the blade being understood, there quickly followed 

 a variety of instruments of the same principle of 

 construction — spears, spades, knives, etc. That is 

 to say, the evolution proceeded in divergent lines, 

 resulting in a differentiation of forms. From these 

 several forms others were again evolved, resulting 

 in a further differentiation. Thus, from the primi- 

 tive form of knife, were derived swords, sickles, cut- 

 lery for table use, etc. The general course of evo- 

 lution was, therefore, toward more and more perfect, 

 and, at the same time, more and more different, 

 forms; in other words, it was progressive and diver- 

 gent. 



The above three principles, so readily comprehen- 

 sible in their application to the simple case of evo- 

 lution we ha\e considered, may be regarded as the 

 fundamental laws of evolution. We shall find that 

 in every instance of evolution — in the world of 

 nature, as well as in the world of human affairs — 

 the process has gone on according to these laws. In 

 many important respects there are great differences 

 indeed between evolution in the one sphere and in 

 the other, but these three laws of the evolutionary 

 process are fundamental and of entirely general 

 application. If the reader has a clear understand- 

 ing of them, he has gained a good notion of what 

 evolution is as a principle. 



This paper may close by pointing out — though, 

 doubtless, it has already occurred to the reader — that 

 the class to which every article of handicraft, or 

 manufacture of any kind, belongs, has had a history 

 of development similar to that we have traced for 

 the class considered. Nothing could be more inter- 

 esting than to imagine, or, if possible, to find out 

 by actual investigation, this developmental liistory 

 for familiar articles. For instance, the evolution of 

 our various sailing vessels, including the modern 

 steamships, from the dug-out log, which served as 

 the boat of primitive man ; or the evolution of car- 

 pets and rugs, from the plaited leaves that covered 

 the ground floors of the huts inhabited by our re- 

 mote ancestors. But it is important to observe that 

 not onl^- ordinary articles of manufacture are pro- 

 ducts of a process of evolution, but every material 

 object made hy human skill. A work of art — a 

 cathedral, for example, — is as much an evolution as 

 any minor article. Only' the cathedral grew out of 

 needs of a higher type — the icsthetic and religious, 

 instead of the merely practical. 



But this is by no means' all. Not only are all 

 material things, fashioned by human skill, products 

 of a process of evolution, but also all human insti- 

 tutions as well. Laws, customs, manners, systems 

 of education and of government — all have come to 

 be as the\ now are by a process of evolution from 

 simple beginnings, originating with primitive man. 

 A study of the history of any one of these institu- 

 tions will show that it has been a development tak- 

 ing place under precisely similar causes, and accord- 

 ing to precisely similar laws, as those of the simple 



illustrative case of evolution we have considered. 

 Take, for instance, our civil laws. With the first 

 recognition and practical observance of the limita- 

 tion of individual rights by primitive man, originated 

 the institution of civil law. These first principles 

 of social life were transmitted to succeeding genera- 

 tions, but were successively, and, upon the whole, 

 progressively, modified, in adaptation to successively 

 better realizations of social relations. Moreover, 

 the first laws were very general — in the nature of 

 broad principles — and from them were gradually 

 derived more specific laws, involving the essence of 

 the original law, but variously modified in adapta- 

 tion to more specific circumstances. For example, 

 the law of property — right of possession — was at first 

 very general in its nature, but gradually gave rise to 

 specific laws, determining rights of property between 

 man and state, husband and wife, etc. That is to 

 sa^', there was both progression and differentiation 

 — advance and divergence — in the development of 

 our, civil laws, and these are characteristics of every 

 process of evolution. Indeed, there could scarcely 

 be a more luminous example of an evolution, than 

 that afforded by the history of ourbody of civil laws. 



Thus we are brought to the broad fact that every 

 productof human labor, skill, thought, orexperience, 

 has come to be what it now is by a process of evolu- 

 tion. Evolution is, therefore, a principle pervading 

 every department of human activity. In the ne.xt 

 paper we shall consider whether this same principle 

 extends also into the domain of nature. 



Union College, Scheneciady, N. Y. 



[Original in Tilt Popular Science irem.} 

 PETROLEUM AND NATURAL GAS. 



The bitumen series is made up of several hydro- 

 carbon compounds, which pass by insensible grada- 

 tions from one into another. Naphtha, which is the 

 first of the series, and which, in some localities, is 

 found flowing out of the earth, is a clear, limpid, 

 and colorless liquid. Petroleum, by further oxida- 

 tion, becomes maltha, or mineral tar, which, 

 in turn, passes into soft asphaltum, and this finally 

 becomes hard and glossy. Natural gas is also a 

 member of this series. 



Petroleum and natural gas, in common with the 

 other members of the group, have probably origi- 

 nated by the decomposition of animal and 

 vegetable matter, deposited in the rocks at the 

 time of their formation. While it is true 

 that they occur in all formations, from the 

 Silurian to the Tertiary, they are found prin- 

 cipally in two geological epochs, the Silurian, 

 and lower half of the Tertiary, being present in only 

 the smallest quantities in other formations. The 

 reason is obvious. The Siluriari age was one in 

 which limestones, shales, sandstones, and clays 

 alternate. The immense thickness of limestones 

 was formed in every case of animal remains, such as 

 shells, corals, crinoids, and minute rhizopods; the 

 oceans teemed with the lower forms of animal life. 

 The sandstones and conglomerates are full of plant 

 remains, indicating by their abundance that im- 

 mense sargasso seas must have existed at the time 

 of their formation. Material for the production of 

 oil and gas existed in abundance. 



In the course of time, this matter was converted 

 into petroleum and natural gas by decomposition, 

 just as such matter, when protected from the atmos- 

 phere while undergoing decomposition, will now 

 yield like products. Occupying a much greater 

 space than did the material from which it originated, 

 and covered by hundreds of feet of rock-masses, it 

 was under a tremendous pressure, and was forced 

 upward. The impervious beds of clay acted as a 

 roof, and, in some places, both oil and gas were 

 thus imprisoned. 



