Vol. XXIII. No. 5.] 



POPULAR SCIENCE NEWS. 



67 



reproduction of both sides of them is de- 

 sired, a second piece of paper, also covered 

 with miicihige, is placed over them ; the 

 whole is placed between several pieces of 

 blotting paper, and pressed strongly together 

 by means of weights, or any simple form of 

 press, — a letter copying press answers nicely, 

 — and left for about twenty-four hours. 



At the end of this time, after the mucilage 

 has become thoroughly dry, the two sheets of 

 paper, now firmly glued together, are removed 

 from the press and the part occupied by the 

 wings very carefully cut out with the scissors 

 leaving only a very narro\v margin of white 

 paper. This margin is very carefully moist- 

 ened with water by the aid of a small camel's- 

 hair brush, when the two pieces of paper will 

 separate, leaving on each a perfect imprint of 

 the wings in their natural colors. The scales 

 have been transferred bodily to the paper. 

 Any small pieces of the wings that may still 

 adhere to the paper can be removed with the 

 point of a needle. 



It is evident that in these transfers we see 

 only the lower surfaces of the scales, which 

 are next to the wings, and in some butterflies 

 this lower surface is of a very different color. 

 To obviate this difficulty, they must be trans- 

 ferred once more so that we may obtain a posi- 

 tive picture, as it were, of the wings. To do 

 this, take some fine spirit varnish, such as is 

 used by photographers, and carefully paint the 

 first copy of the wings with it ; then lay it 

 face downwards upon a piece of heavy glazed 

 paper or cardboard, and put it in the press until 

 the varnish has dried, after which by moistening 

 with water, the first piece of paper may be re- 

 moved, leaving the image of the wings on the 

 cardboard, right side up, and in the natural 

 colors. It is then only necessary to dry it, 

 paint in the body of the butterfly, and give it 

 another thin coat ot varnish as a protection. 

 In some species of moths the long hairs with 

 which the bod}' is covered, may be shaved off 

 and added to the drawing with good effect, 

 or, with large specimens, portions of the skin 

 itself ma)' be removed and used in the same 

 way. Usually, however, it will be sufficient 

 to draw or paint the outlines of the body on 

 the cardboard, in the blank space between the 

 transferred images of the wings. 



It sometimes happens, especially in the case 

 of butterHies of a blue color, that the la\ers 

 of scales absorb some of the mucilage so as 

 to change their color almost to a black. The 

 only remedv for this is to remove the gum by 

 careful and continued washing, and the final 

 varnishing must be omitted. The success of 

 the whole process depends upon the care and 

 skill with which it is conducted, but when 

 the art is once acquired, it will prove a source 

 of much pleasure, and the transferred speci- 

 mens ma)- even be of scientific value, as they 

 can be easier preserved than the dried insects 

 themselves, and are not liable to be injured 



by the numerous parasites or accidents, which 

 so often destroy collections in museums and 

 elsewhere. 



[Original in The Popular Science News. I 

 EVOLUTION. 



BY PROFESSOR JAMES H. STOLLER. 



SECOND PAPER. 



EVOLUTION IN PHYSICAL NATURE. 



In the first paper we saw that everything that be- 

 longs to the world of human affairs, whether mate- 

 rial objects or social institutions, is the product of a 

 process of evolution. We are now to extend our 

 inquiry into the realm of nature, and see whether 

 the same law is in operation there. In the present 

 paper we shall consider the question only as it 

 relates to physical nature, that is, to the earth, and, 

 so far as may be, to the heavens, with the countless 

 worlds, surrounding us. Our study, therefore, re- 

 lates — first, to the evolution of the Earth, and 

 second, the evolution of the Cosmos. 



The Earth. — Definitely stated, our inquiry is, 

 whether the globe on which we live has come to be 

 as it now is by a process of progressive change from 

 a primal unorganized (homogeneous) earth-mass. 

 Or, to use an illustration with which we are now 

 familiar, whether the earth has been derived from a 

 primordial mass by a process of gradual formation 

 (under natural agencies), in a way similar to that 

 by which every form of cutting-instrument has been 

 derived (under human agencies) from the ancient 

 stone axe. 



This illustration will also help us to understand 

 the nature of the evidence upon which the answer 

 to our inquiry rests. The main fact of the evidence 

 showing the evolution of cutting-instruments is, 

 that we are able to trace a succession of forms from 

 the original instrument to those of to-day. Now we 

 are able to do the same thing in respect to the earth ; 

 we are able to see very clearly, by means of the 

 record preserved to us in its structure, that its his- 

 tory has been one of progression, through succes- 

 sive stages, from a simple primitive form to the 

 complex form which it now has. It is true that the 

 successive forms through which the earth has passed 

 have not been separately preserved, as have been 

 the successive fonns of cutting-instruments. In the 

 case of the latter, as we saw in the first paper, it 

 would be possible to arrange the different forms in a 

 series, showing clearly the successive steps of the 

 evolution. But in the case of the earth, such a 

 series of separate terms does not exist. The series 

 is consolidated — the successive forms are superim- 

 posed and united into a whole. The difference is 

 this : In the one case, evolution occurred by the 

 successive substitution of terms; in the other case, 

 by successive modifications of the original term. 

 Hence the result of the process in the former mode 

 of occurrence is a series of separate forms, bearing 

 no marks of their origin ; in the latter, a single 

 form, but bearing distinct marks of the successive 

 states through which it has passed. It is obvious 

 that the evidence of evolution in the latter case is 

 even more convincing than in the former. As the 

 rings of a tree, seen in a section of its trunk, prove 

 growth, so the rock formations, seen in a section of 

 the earth's crust, prove its evolution. 



In order to understand clearly the fact of the 

 earth's evolution, it is only necessary to give atten- 

 tion to the ordinary operations of nature, now going 

 on about us, and then to consider the effects of these 

 operations, as agents in building up the earth in 

 past ages. We have only to assume that causes sim- 

 ilar to those now in operation have been in action in 

 all past time — in other words, that the forces of 

 nature (heat, gravitation, chemical affinity, etc.) are 



permanent forces — to be forced to conclude that the 

 earth has been built up gradually and progressively. 

 Let any one study the effects produced by natural 

 agencies now in action — the flow of rivers, the 

 movements of winds and tide, the action of rain and 

 frost, the disturbances produced by earthquakes and 

 volcanoes, the various other operations brought 

 about by physical and chemical forces — and then let 

 him reflect that these agencies have been producing 

 the same effects in all past time, and he will realize 

 that the earth's history has been one of continuous 

 development, that is to say, of evolution. For ex- 

 ample : We see now that atmospheric gases decom- 

 pose rocks into soils, and that rains wash the soils 

 into rivers, by which they are carried to the sea and 

 deposited as sediments. Careful observation also 

 shows that these sediments, having undergone con- 

 solidation at the sea-bottom, are oflen upraised and 

 added to the land-sm-face. Now we have every 

 reason to believe that these processes have gone on 

 during all past time, and thus we understand in 

 what way the gradual building up of the continents 

 has taken place. 



But we are not left to mere a priori reasoning to 

 prove that our earth is the product of an evolution. 

 The question is forever settled by the evidence fur- 

 nished in its structure. The rock-strata which form 

 its crust constitute a record of its history which is 

 beyond question ; for it is a record whose authen- 

 ticity is the absoluteness of nature. We have but to 

 notice two or three features of her framework of 

 rock, to understand how it tells the story of the 

 earth's evolution. 



1. The rocks which compose the earth's crust, 

 excepting those that are obviously of volcanic ori- 

 gin, are stratified. This is absolute proof that they 

 were formed under water; that is to say, they were 

 formed either by the consolidation of sediments 

 brought down by rivers as detritus from the land, or 

 by the slow accumulation of the hard remains of 

 organisms inhabiting the water, as corals, molluscs, 

 etc. By the former process were formed sandstones 

 and shales; by the latter, limestones and chalk. 

 But these rocks which were formerly under water — 

 that is, were sea-bottom — are now land-surface. 

 Therefore, all lands have been formed by elevation 

 of the sea-bottom. Keeping this fact in mind, let 

 us next observe that rocks now far inland often 

 show unmistakable evidences of former coast-lines. 

 Such evidences are ripple-marks, sun-cracks, worm- 

 tubes, and tracks of animals. The position of these 

 lines is usually such as to show that they marked 

 successive sea-limits, the ocean being pushed back 

 step by step. Now, take this fact in connection with 

 the one just mentioned — that all lands have been 

 formed by elevation of the sea-bottom — and we have 

 conclusive evidence of the evolution of the conti- 

 nents : to the primordial land-mass, upheaved from 

 the sea, there were added, in slow succession, area 

 after area, likewise raised from the sea, until the 

 present extent of land-surface was reached. Doubt- 

 less there were occasional interruptions in the pro- 

 cess, — areas of land, rescued from the sea, sank 

 again beneath the waters, and the work of elevation 

 had to be done anew, — but, upon the whole, we may 

 say with certitude, that the process of continent- 

 making was steadily progressive. 



2. The rocks show not merely that the continents 

 attained their present extent by a progressive up- 

 rising of the land, but also that all their features- 

 mountains, plains, valleys, lakes, and rivers — came 

 to be as they now are by a gradual process. By 

 studying the arrangement of the rock-strata, keep- 

 ing in mind that the lowest are the oldest, and that 

 discontinuity or unconformity indicates a lost inter- 

 val, it is often possible to trace clearly the successive 



