A4 



The Ottawa Naturalist 



[Vol. XXXII. 



All of these may, and have for that matter, be- 

 come fossils; it is only necessary that the mud or 

 the tar or the sand or the resin or the ice shall be 

 preserved (obviously it can not be washed away or 

 destroyed without destroying the fossil), and that 

 the footprint or the shell or the bone or the leaf, or 

 its impression, shall be preserved as well. This is 

 made easy by the hardening of the mud or sand 

 into rock, a process which is sure to follow if the 

 material is given enough time. If the jelly-fish can 

 hold its shape until the layer of mud has hardened, 

 smaller particles will gradually filter into the cavity 

 which it leaves, and these may be different enough 

 from those around it so that when the rock is split 

 apart on this particular layer the shape of the jelly- 

 fish can be seen. The cavity may even become 

 filled with calcite or a similar mmeral. The two 

 Invers of mud that pressed the upper and under 

 sides of the leaf may show its form and outline even 

 though the leaf decay. On the other hand the shell 

 or the bone, or even the entire body, as in the case 

 of the mammoth, may be preserved as it is, without 

 change. Sometimes, however, only the tube or bur- 

 row in which the animal lived is preserved. 



Still another way in which fossils may be pre- 

 served is best described by supposing that you were 

 to change a picture, a mosaic, which owed its 

 features to the skilfuU arrangement of differently 

 colored berries by substituting for each berry a 

 pebble of the same shape, size, and color. You 

 would have changed nothing about the picture but 

 Its lasting qualities, you would have mad" it safe 

 from decay. It is this process in nature but on a 

 very much smaller scale which has given us such 

 fossils as petrified wood. The exchange of par- 

 ticles IS here so fine that the smallest details of 

 structure are preserved and may be studied under 

 the microscope. 



Now many of the softer rock deposits are ex- 

 posed at the surface of the earth and man has cul- 

 tivated the layer of soil immediately above, but 

 they were laid down, formed, ages ago and during 

 the lifetime of the animals and plants whose remains 

 can now be found in them. As we have said these 

 are the real fossils. If a farmer living on such a 

 soil should dig down three or four feet and bury a 

 dog that dog would not become a fossil even though 

 the bones did not decay and were to be dug up 

 thousands of years later together with the remains of 

 the real fossils. It did not get where it is in the 

 ordinary course of events, man put it there. If the 

 real fossils were dog bones it might be difficult to 

 separate the fossil dog bones from the farmer-buried 

 dog bones. But it would be almost impossible to 

 mix a group of animals that had lived on the earth 

 for any great length of time prior to another with 



that other, so that the fossil expert, for whom the 

 term paleontologist is in common use, could not 

 detect the mixing. If one bone or shell did not give 

 the fact away another would, and even the two sets 

 of dog bones would probably differ from each other, 

 for animals and plants have always changed from 

 age to age. It is this progressive change in time 

 which we call evolution. 



If the person who dug up the fossil bones and 

 the farmer-buried dog bones had looked closely he 

 would have seen that the earth around the farmer's 

 dog had been disturbed, that the lines of bedding 

 (stratification) in the nearby rock stopped some dis- 

 tance from the dog and that the earth near it was 

 jumbled together; also that this was not true with 

 regard to the bedding near the fossils. It is this care 

 in collecting and attention to detail which is natural 

 to paleontologists, and which others must make use 

 of when they collect fossils if these are to have any 

 value. Many of the doubtful points in the earth's 

 history, such as whether the human bones which 

 have been found in certain places in our West, or 

 in Argentina, are those of primitive man or those 

 of recent natives were made doubtful by carelessness 

 or lack of observation on the part of the person who 

 first made the discovery. 



Nature has been very careful about recording 

 what she has done, however careless she may be 

 in destroying that record, and fossils may be 

 likened to the hieroglyphics which the Egyptians 

 used to carve, in more ways than one. They, 

 the fossils, are Nature's handwriting, her method 

 of labelling the rocks of the earth's crust, and 

 while fossil hieroglyphics are sometimes hard to 

 read, and while they, like those of Egypt, mean 

 little or nothing to the ordinary person, their 

 story IS easily read by the man who knows. 



Perhaps we can better illustrate the use of fossils 

 by comparing them to the documents placed in the 

 foundation stones of buildings. It is customary to 

 seal up in such stones objects like the daily papers of 

 the date upon which the stone is laid, coins, etc., 

 anything which will indicate to the one who opens 

 the vault, whether this be done in a hundred or a 

 million years, and when every other evidence as to 

 the age of the building may have been lost, the exact 

 period of the earth's history during which the build- 

 ing was erected. Nature has sealed up in rocks of 

 all ages but the oldest, in all but a few varieties, and 

 in nearly all places, articles (fossils) which convey 

 an accurate idea of the relative time at which the 

 different rocky tombs were built, and we are daily 

 becoming more expert in reading the story they tell. 



Since fossil experts in all countries are continually 

 at work on these problems, and since an expert in 

 Japan, for example, should know exactly what a 



