Dec. 7, 1888.] 



SCIENTIFIC NEWS. 



589 



away by the weather. Some of the bands stood out in 

 relief, while others were worn into curves. They might 

 even find banded flints which were often mistaken 

 for true fossils. Now he must refer them to the fact 

 that flints sometimes possessed some other curious 

 characteristics. There was a bed at Charlton, North 

 Woolwich, where it looked as if there were flints ; if 

 one picked away the chalk the flint tumbled into a 

 large number of little pieces. This showed that, through 

 some upheaval, probably, the flint had been smashed 

 to pieces, but the chalk had held every portion 

 in its place, and they did not see that the 

 flint was smashed up until they removed the sur- 

 rounding chalk. The fact was that the beds had been 

 subjected to great movements, and during the move- 

 ments the crushing operations had taken place, but the 

 flints had not been able to fall to pieces, on account of 

 the surrounding chalk. Sometimes one came across a still 

 more curious circumstance — a flint had been sometimes 

 broken up into pieces, and fragments had been more or 

 less displaced, but after the displacement the flint had been 

 cemented together again, and so perfectly mended, that 

 if one tried to break it it would break anywhere except 

 along the original fracture — just as it was said that if a 

 man's arm was broken, if he had an accident again it 

 would not break again in the same place. So with 

 fractured flints. It was evident that a remarkable 

 process of fracture and mending had gone on in the 

 flints. 



He must next call attention to the fact that flints 

 not unfrequently contained fossils, that was, remains of 

 animals and plants that had once lived, and a very great 

 number of fossils had been found in flints. Those 

 fossils sometimes occurred in one way, and sometimes 

 in another. Sometimes the fossil was a wonderful 

 replacement of the original shell ; sometimes they got 

 what looked exactly like an ordinary shell, which they 

 knew to consist of calcic carbonate, and when they ex- 

 amined them carefully, instead of consisting of calcic 

 carbonate which dissolved easily in vinegar or other 

 acid, they found it consisted of the totally different 

 substance, silica. That those shells such as oysters and 

 other well-known forms of shell were once formed of 

 the substance calcic carbonate there could not be the 

 slightest doabt. The whole of the original substance of 

 the shell had been dissolved away, particle by particle, 

 and another particle of silica had been put in the place 

 of the several particles of calcic carbonate, that is chalk 

 matter, until the whole mass had been converted into 

 silica or flint. But at other times it was evident that the 

 process of making the fossil had gone on in a totally 

 different way. Some fossils exhibited were evidently 

 remains of shells of sea urchins, but if they examined 

 them they found that the shell had not been preserved, that 

 they had a cast or impression of the inside and another cast 

 of the outside, and the place where the shell itself was, 

 was now perfectly hollow, as in cases such as exhibited. 

 So that when they got a perfect fossil they had the 

 cast lying in the midst of the flint, and the 

 space occupied by the original shell had been completely 

 dissolved away. In a specimen exhibited they got the 

 outside shell perfectly impressed on the flint. Inside 

 the shell every little hole and marking most perfectly 

 preserved an exact impression such as one would be 

 able to take with sealing-wax or plaster of Paris in the 

 midst of the shell. Then in another case exhibited they 

 had an external cast and an internal cast. He would 



have to refer more particularly to these casts, and the 

 way in which they originated in a future lecture. Some- 

 times they found that the shell, like one produced, 

 resembling the great pinnae that lived at the present 

 day, had been worn away, but while the shell was 

 living, sponges, which made their home in shells, had 

 burrowed into the substance of the shell. These burrows 

 had been filled by white chalk mud, which filled the 

 fossil originally. Now a curious thing had occurred. 

 This chalk had been converted into flint, but the sub- 

 stance of the shell was removed, and thus perfect casts 

 were obtained of those wonderful burrows. They would 

 find subjects of infinite interest and variety in the study 

 of those curious fossils which occurred in flint, especially 

 if, as he hoped to be able to point out, they could reason 

 as to why in some cases they got a cast, and in other 

 cases got the actual replacement of the shell. 



He must now ask them to direct their attention from the 

 flints to the chalkin which the flints occurred. That chalk 

 - — as they were all aware now the subject had been so 

 frequently explained — had a most wonderful resemblance 

 to the white mud which was found occurring at the 

 bottom of the Atlantic, and which was brought home by 

 the Challenger. This mass contained a quantity of sticky 

 material known as globigerina ooze, which covered a 

 large portion of the bottom of the Atlantic. It was not 

 quite so white as chalk, but in other respects it re- 

 sembled somewhat grey chalk reduced to powder. If 

 they placed some fragments of chalk which had been 

 washed carefully and some of the globigerina ooze under 

 a microscope, it would be seen that they presented a 

 most wonderful resemblance. What he had now to call 

 their attention to was that, if they examined this Atlantic 

 ooze and chalk much more carefully, they would find 

 that Atlantic ooze contained objects which were not 

 found in the chalk. If they dissolved away with a little 

 vinegar or other acid, the chalk would have very little 

 left. If they took Atlantic ooze, and with a little vinegar 

 or other acid dissolved away the shells, which were com- 

 posed of calcic carbonate, they would in most cases find 

 left behind a great number of minute objects, and if 

 they were examined they would be found to be 

 very interesting objects indeed. A careful exami- 

 nation would show that they were composed of silica 

 — that kind which was called colloidal silica, and when 

 they came to look at their forms it would be seen that 

 they were very definite structures indeed. They were 

 skeletons of curious organisms, some of which were plants 

 and some animals. The plant formations were very 

 minute forms indeed. Drawings of the very beautiful 

 forms known as the diatomaceae, which had skeletons 

 composed of colloidal silica. Every little plant was simply 

 a little cell, and consisted ot a membrane containing 

 a liquid, but each of those little cells had the power of 

 secreting a skeleton which was of very curious form. 

 It consisted of three portions like a box. First there were 

 two discs, which were sometimes round and sometimes 

 had very curious shapes as represented in other figures, 

 and between them there was a double girdle so 

 that the two parts fitted into one another. These 

 skeletons were so excessively minute that they could 

 only make out the forms and marking with a very 

 h'gh power microscope — a power of | inch or ^th inch 

 or even higher power. If they examined them with such 

 high powers it would be found they were covered with 

 most beautiful patterns and markings, something like 

 specimens shown in a diagram, which, however, repre- 



