hunter's posthumous paper on fossils. 299 



by operations of inorganic nature. It has become a distinct branch of 

 the science of fossil remains, under the name of ' Ichnology' 1 . 



" Vegetables," he says, " are formed only on the land." By this 

 Hunter probably meant that, whether they grew in an atmosphere of 

 air or water, they grew on and from the earth ; as the sea-weeds of our 

 coast are attached by their discoid roots to rocks and stones, and the more 

 obvious freshwater plants grow, also, from the bottom. There are, how- 

 ever, exceptions to this rule : a very large one — the floating ' Sargasso ' 

 of the Gulf-stream — had escaped the memory of Hunter ; this sea- weed 

 is generated and developed in the ocean, as freely, as independently of its 

 bottom, as the whales and fishes that are born or brought forth free, 

 and, as Hunter states, are ' formed in the sea.' 



I would next request your attention to Hunter's idea of the proper 

 end and limits of the study of geology and fossil remains : — " This 

 investigation," he tells us, " has nothing to do with the original forma- 

 tion of the earth itself; but has only a connexion with the changes 

 on its surface." 



1 [''There are several circumstances under which impressions made on a part of 

 the earth's surface, soft enough to admit them, may be preserved after the impressing 

 body has perished. "When a shell sinks into sand or mud, which in course of time 

 becomes hardened into stone, and when the shell is removed by any solvent that 

 may have filtered through the matrix, its place may become occupied by crystalline 

 or other mineral matter, and the evidence of the shell be thus preserved by a cast, 

 for which the cavity made by the shell has served as a mould. If the shell has sunk 

 with its animal within it, the plastic matrix may enter the dwelling-chamber as far 

 as the retracted soft parts will permit ; and as these slowly melt away, their place 

 may become occupied by crystallized deposits of any siliceous, calcareous, or other 

 crystallizable matter that may have been held in solution by water percolating the 

 matrix, and such crystalline deposit may receive and retain some colour from the 

 soft parts of which it thus becomes a cast. 



" Evidences of soft-bodied animals, such as Actinia and Medusa, and of the excre- 

 mental droppings of higher animals, have been thus preseiwed. Fossil remains, as 

 they are called, of soft plants, such as sea-weeds, reeds, calamites, and the like, are 

 usually casts in matrix made naturally after the plant itself has wholly perished. 



" Even where the impressing force or body has been removed directly or shortly 

 after it has made the pressure, evidence of it may be preserved. A superficial film 

 of clay, tenacious enough to resist awhile the escape of a bubble of gas, may retain, 

 when petrified, the circular trace left by the collapse of the burst vesicle. The 

 lightning flash records its course by the vitrified tube it may have constructed out of 

 the sandy particles melted in its swift passage through the earth. The hailstone, 

 the ripple wave, the rain-drop, even the wind that bore it along and drove it slanting 

 on the sand, have been registered in casts of the cavities which they originally made 

 on the soft sea-beach ; and the evidence of these and other meteoric actions, so written 

 on imperishable stone, have come down to us from times incalculably remote. Every 

 form of animal life that, writhing, crawling, walking, running, hopping, or leaping, 

 could leave a track, depression, or footprint behind it, might thereby leave similar 

 lasting evidence of its existence, and also to some extent of its nature." — Owen's 

 • Paleontology,' 8vo, 1860, p. 152.] 



