530 Henry Woodivard — Address to the Geologists^ Association. 



mineralogically combined, and at tlie same time affords valuable in- 

 formation as to the intimate physical structure and arrangement of 

 the components of the rock-mass, tending to elucidate its formation 

 and origin." ' 



(&.) For the second he requires a knowledge of all those various 

 physical forces by which matter is affected, as, for instance, gravita- 

 tion, producing pressure, which in its turn is converted into heat, and 

 results in expansion, to be again followed by cooling and contraction. 



Moreover he must study the attendant cosmical effects of solar 

 light, heat, and attraction upon our earth, resulting in seasonal and 

 diurnal variations in temperature, with the ceaseless aerial circulation 

 of aqueous vapours from sea to mountain, to be again returned to 

 " the mother of waters," the mighty ocean, as snow and ice, rain 

 and rivers, laden with those solid and soluble ingredients to which 

 all our sedimentary rocks owe their origin. 



II. — By Paleontology we comprehend the study of the various 

 forms of plants and animals which inhabited our earth in past 

 geologic epochs, from the earliest Palceozoic times down to our own 

 day. This again may naturally be subdivided into : — (a.) FaloBo- 

 phytology; and (b.) Palceozoology. 



(a.) In order to pursue Palceophytology with success, we must be 

 acquainted with the economy, structure, classification, and distri- 

 bution of living ]Dlants. An intimate acquaintance with their 

 structure is of the first importance; for the Palfeophytologist has to 

 base his determination not unfrequently u})on the impress of a leaf, 

 the cortical scars upon a trunk, a detached seed-vessel, or the 

 structure of the mineralized woody tissue of a stem. 



(6.) In Palceozoology a similar knowledge of living animals is 

 requisite ; and here again it is needful to take with us an intimate 

 acquaintance with their anatomical structure, and indeed with every 

 detail of their organism. For the palaeontologist is often required 

 to throw light upon the nature and habits of an animal upon the 

 discovery of a single vertebra, or a limb-bone, or upon the fragment 

 of a jaw, or even upon a single tooth or feather : whilst amongst the 

 lower forms of invertebrate life, the wing of a Dragon-fly, the elytron 

 of a Beetle, the fragment of a Star-fish or a Crinoid, or the shelly 

 covering of a Crustacean or Mollusk, may be all that he has to guide 

 him in giving it a place and name. 



Yet — incredible as it may seem — the oft-controverted, oft- verified, 

 labours of Owen, Edward Forbes, Falconer, Huxley, Salter, Heer, 

 Davidson, Williamson, Carruthers, and many other workers in 

 Palasontology, attest the reliability of their results when based (as 

 all good work of the kind must ever be) upon a careful and compre- 

 hensive study of living forms. 



I.— Geology. 



(a.) Petrology. — No class of rocks offers such varied and marvel- 

 lous attraction for the speculative and theoretical geologist as do those 



1 "The Microscope in Geology," by David Forbes, F.R.S., Popular Science 

 Eeview, 1867, vol. vi. p. 355. 



