HARDWICKE'S SCIENCE-GOSSIP. 



99 



strated, the physical changes everywhere going on 

 at the present day, do not differ in their nature, and 

 probably not in their intensity, from those which 

 took place in former geological periods. But, un- 

 doubtedly, the nature of geological study obliges 

 the young beginner first of all to pick up aji ele- 

 mentary knowledge of natural history. How can 

 he understand anything of the fossil plants, shells, 

 bones, teeth, &c, he meets with so abundantly in 

 every formation, unless lie knows something 

 about similar recent objects ? Possils only differ 

 from their modern representatives in being an 

 extinct zoology or botany, instead of an existing one. 

 Thus is the geological student forced to contiuually 

 widen his sphere of research, and he finds that every 

 additional bit of knowledge of any other natural 

 science helps him all the more to understand that 

 which he bas selected as his special hobby. 



Geology is essentially an open-air study. It 

 leads a man into the most beautiful of landscapes, 

 to the most charming of scenery. The tame flatness 

 of the plains reveals to him comparatively little, un- 

 less coal- or salt-mining has partly turned the earth's 

 crust inside out, or railway cuttings have laid open 

 sections instructive both as regards the strata 

 and the fossils they contain. Boulder-claypits or 

 natural tarns will even here occasionally prove in- 

 teresting. But to study the stony science in its 

 fulness we must " gang to tbe hills ! " There, 

 ■where tbe heather is purplest, and tbe atmosphere 

 exhilarates like old wine, you are most likely to 

 read off the " record of the rocks ! " Healthful ac- 

 tivity is necessarily gendered ; and the memory is 

 stored with remembrances of sunny days and clear 

 skies, never to be forgotten ! 



In the course of the following articles we purpose 

 introducing the young student to the " happy 

 hunting-grounds" of our various geological forma- 

 tions. Perhaps some of our many readers will assist 

 in the catalogue of geological collecting-grounds, and 

 any information thus given we shall gladly publish. 

 At the same time, we purpose limiting ourselves 

 to the common fossils, unless we are occasionally 

 tempted to mention a few for tbe purpose of further 

 •whetting the appetite. And, whilst we describe 

 the spots where tbe young geologist is most likely 

 to " make a bag," we propose giving a brief descrip- 

 tion of tbe natural history relationships of the 

 numerous extinct organisms. 



Commencing with the most lowly organized, we 

 pass over the fossil known as Eozoon ; first, because 

 its organic nature is still held to be doubtful, 

 although the balance of evidence is decidedly in its 

 favour. " Eozoonal structure," as it is now termed, 

 is not confined to tbe oldest Laurentian rocks. 

 Professor King has discovered it in the Ophites, or 

 metamorphosed Liassic rocks of the island of 

 Lewis. It is also abundant in the green crystal- 

 line marbles, of Lower Silurian age, in Connemara, 



in Ireland. Now, the distribution of lowly organized 

 forms can never be safely accepted as indicating 

 the age of a rock. Naturalists are well aware that 

 the most lowly organized animals and plants are 

 just those which have bad the widest distribution 

 both in time and space. It is the most highly 

 organized species of animals and plants that best 

 mark the geological ages of formations. So that 

 tbe fact of finding " Eozoonal structure " in lime- 

 stones other than the Laurentian, is of itself no 

 evidence against the animal nature of the Eozoon. 



Even as regards another fossil (named after Pro- 

 fessor Oldham), geologists have long been in doubt 

 as to its nature, whether it was animal or vegetable. 

 It is called a Zoophyte, an unfortunate designation, 

 which often conveys to illiterate or half-read people 

 the idea that sucb objects are partly animal and 

 partly vegetable. The name originally was intended 

 only to express their external resemblances to 

 plants; but it is constantly twisted to signify a 

 hybrid combination of animal and vegetable cha- 

 racters. As regards the Oldhamia— ike fossil about 

 which we are now speaking — it has been alternately 

 regarded as a seaweed or a zoophyte. Mr. Salter 

 thought that possibly it was a calcareous or limy 

 seaweed, like the common Corallina officinalis, 

 wbich you may find so abundantly in every rock- 

 pool at low-water. The latter is undoubtedly a 

 seaweed ; but its limy structure and jointed stem 

 caused it to be regarded by the earlier naturalists 

 as a Coralline ; whence its name. Professor Edward 

 Porbes believed that the Oldhamia showed, at the 

 articulations of the stems, the positions of the 

 minute cells of the zoophytes. The most likely 

 idea is that this very pretty and interesting fossil — 

 the oldest organic form with which we are certainly 

 acquainted— was related to the little "sea-firs" 

 that are so abundant nowadays along our coasts. 

 Indeed, not a few of these Sertularians (as they are 

 called) resemble in external shape the Oldhamia. 

 The dry portion that remains when the zoophytes 

 are dead, is of a homy nature, and formed of a sub- 

 stance termed Chitine. Now this is one of the 

 most indestructible of animal substances, and is 

 likely to be preserved when others would be decom- 

 posed. If the Oldhamia had been calcareous, the 

 limy matter would speedily have been dissolved 

 away, and few or no traces of them would have 

 been left. We think, therefore, that the most pro- 

 bable natural history position of the Oldhamia is 

 among the Hydrozoa, of which the " sea-firs " (com- 

 monly mistaken for seaweeds), which you may see so 

 abundantly clustering on the backs of old oyster- 

 shells in any fishmonger's shop, are the most 

 familiar examples. The Graptolites, which are so 

 numerous in the Lower Silurian rocks, as we shall 

 presently see, belonged to the same class. 



There are two species of Oldhamia known to 

 geologists, each distinctly marked from thejother. 



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