420 



NATURE 



\Sept. 9, 1875 



direct their attention to the general relations existing among all 

 the forces and phenomena of nature. In some important branches 

 of such subjects, it is only through study of the local physical 

 conditions of various parts of the earth's surface and the compli- 

 cated phenomena to which they pive lise, that sound conclusions 

 can be established ; and this study constitutes physical or scien- 

 lific geography. It is very necessary to bear in mind that a 

 large portion of the phenomena dealt with by the sciences of 

 observation relates to the earth as a whole in contradistinction to 

 the substances of which it is formed, and can only be correctly 

 appreciated in connection with the terrestrial or geographical 

 conditions of the place where they occur. On the one hand, 

 therefore, while the proper prosecution of the study of physical 

 geography requires a sound knowledge of the researches and 

 conclusions of students in the special branches of science, on the 

 other success is not attainable in the special branches without 

 suitable apprehension of geographical facts. For these reasons 

 it appears to me that the general progress of science will involve 

 the study of geography in a more scientific spirit, and with a 

 clearer conception of its true function, whicli is that of obtaining 

 accurate notions of the manner in which the forces of nature 

 have brought about the varied conditions characterising the sur- 

 face of the planet which we inhabit. 



In its broadest sense science is organised knowledge, and its 

 methods consist of the observation and classification of the 

 phenomena of which we become conscious through our senses, 

 and the inves-tigation of the causes of which these are the effects. 

 The first step in geography, as in all other sciences, is the obser- 

 vation and description of the phenomena with which it is con- 

 cerned ; the next is to classify and compare this empirical collec- 

 tion of facts, and to investigate their antecedent causes. It is 

 in the first branch of the study that most progress has been 

 made, and to it indeed the notion of geography is still popularly 

 limited. The other branch is commonly spoken of as physical 

 geography, but it is more correctly the science of geography. 



The progress of geography has thus advanced from first rough 

 ideas of relative distance between neighbouring places, to correct 

 views of the earth's form, precise determinations of position, and 

 accurate delineations of the surface. The first impressions of 

 the differences observed between distant countries were at length 

 corrected by the perception of similarities no less real. The 

 characteristics of the great regions of polar cold and equatorial 

 heat, of the sea and land, of the mountains and plains, were 

 appreciated ; and the local variations of season and climate, of 

 wind and rain, were more or less fully ascertained. Later, the 

 distribution of plants and animals, their occurrence in groups of 

 peculiar structure in various regions, and the circumstances under 

 which such groups vary from place to place, gave rise to fresh 

 conceptions. Along with these facts were observed the pecu- 

 liarities of the races of men— their physical form, languages, 

 customs, and history — exhibiting on the one hand striking differ- 

 ences in different countries, but on the other often connected by 

 a strong stamp of similarity over large areas. 



By the gradual accumulation and classification of such know- 

 ledge the scientific conception of geographical unity and continuity 

 was at length formed, and the conclusion established that while 

 each different part of the earth's surface has its special charac- 

 teristics, all animate and inanimate nature constitutes one general 

 system, and that the particular features of each region are due to 

 the operation of universal laws acting under varying local condi- 

 tions. It is upon such a conception that is now brought to bear 

 the doctrine, very generally accepted by the naturalists of our 

 own country, that each successive phase of the earth's history, 

 for an indefinite period of time, has been derived from that which 

 preceded it, under the operation of the forces of nature as we 

 now find them ; and that, so far as observation justifies the 

 adoption of any conclusions on such subjects, no change has ever 

 taken place in those forces, or in the properties of matter. This 

 doctrine is commonly spoken of as the doctrine of evolution, 

 and it is to its application to geography that I wish to direct 

 your attention. 



I desire here to remark that in what I am about to say, I 

 altogether leave on one side all questions relating to the origin 

 of matter, and of the so-called forces of nature which give rise 

 to the properties of matter. In the present state of knowledge 

 such subjects are, I conceive, beyond the legitimate field of phy- 

 sical science, which is limited to discussions directly arising on 

 facts within the reach of observation, or on reasonings based on 

 such facts. It is a necessary condition of the progress of know- 

 ledge that the line between what properly is or is not within the 

 reach of human intelligence is ill defined, and that opinions will 



vary as to where it should be drawn ; for it is the avowed and 

 successful aim of science to keep this line constantly shifting by 

 pushing it forward ; many of the efforts made to do this are no 

 doubt founded in error, but all are deserving of respect that are 

 undertaken honestly. 



The conception of evolution is essentially that of a passage to 

 the state of things which observation shows us to exist now, from 

 some preceding state of things. Applied to geography, that is 

 to say to the present condition of the earth as a whole, it leads 

 up to the conclusion that the existing outlines of sea and land 

 have been caused by modifications of pre-existing oceans and 

 continents, brought about by the operation of forces which are 

 still in action, and which have acted from the most remote past 

 of which we can conceive ; that all the successive forms of the 

 surface — the depressions occupied by the waters, and the eleva- 

 tions constituting mountain-chains — are due to these same forces ; 

 that these have been set up, first, by the secular loss of heat 

 which accompanied the original cooling of the globe ; and 

 second, by the annual or daily gain and loss of heat received 

 from the sun acting on the matter of which the earth and its 

 atmosphere are composed ; that all variations of climate are 

 dependent on differences in the condition of the surface ; that 

 the distribution of life on the earth, and the vast varieties of its 

 forms, are consequences of contemporaneous or antecedent 

 changes of the forms of the surface and climate ; and thus that 

 our planet as we now find it is the result of modifications gradu- 

 ally brought about in its successive stages, by the necessary 

 action of the matter out of which it has been formed, under the 

 influence of the matter which is external to it. 



I shall state briefly the grounds on which these conclusions 

 are based. 



So far as concerns the inorganic fabric of the earth, that view 

 of its past history which is based on the principle of the per- 

 sistence of all the forces of nature may be said to be now uni- 

 versally adopted. This teaches that the almost infinite variety 

 of natural phenomena arises from new combinations of old forms 

 of matter, under the action of new combinations of old forms of 

 force. Its recognition has, however, been comparatively recent, 

 and is in a great measure due to the teachings of that eminent 

 geologist, the late Sir Charles Lyell, whom we have lost during 

 the past year. 



When we look back by the help of geological science to the 

 more remote past, through the epochs immediately preceding 

 our own, we find evidence of marine animals— which lived, 

 were reproduced, and died, — possessed of organs proving that 

 they were under the influence of the heat and light of the sun ; 

 of seas whose waves rose before the winds, breaking down cliffs, 

 and forming beaches of boulders and pebbles ; of tides and 

 currents spreading out banks of sand and mud, on which are left 

 the impress of the ripple of the water, of drops of rain, and of 

 the track of animals ; and all these appearances are precisely 

 similar to those we observe at the present day as the result of 

 forces which we see actually in operation. Every successive 

 stage, as we recede in the past history of the earth, teaches the 

 same lesson. The forces which are now at work, whether in de- 

 grading the surface by the action of seas, rivers, or frosts, and 

 in transporting its fragments into the sea, or in reconstituting the 

 land by raising beds laid out in the depth of the ocean, are 

 traced by similar effects as having continued in action from the 

 earliest times. 



Thus pushing back our inquiries we at last reach the point 

 where the apparent cessation of terrestrial conditions such as now 

 exist requires us to consider the relation in which our planet 

 stands to other bodies in celestial space ; and vast though the 

 gulf be that separates us from these, science has been able to 

 bridge it. By means of spectroscopic analysis it has been 

 established that the constituent elements of the sun and other 

 heavenly bodies are substantially the same as those of the earth. 

 The examination of the meteorites which have fallen on the 

 earth from the interplanetary spaces, shows that they also con- 

 tain nothing foreign to the constituents of the earth. The in- 

 ference seems legitimate, corroborated as it is by the manifest 

 physical connection between the sun and the planetary bodies 

 circulating around it, that the whole solar system is formed of 

 the same descriptions of matter, and subject to the same general 

 physical laws. These conclusions further support the sup- 

 position that the earth and other planets have been formed by 

 the aggregation of matter once diffused in space around the sun ; 

 that the first consequence of this aggregation was to develop 

 intense heat in the consolidating masses ; that the heat thus 

 generated in the terrestrial sphere was subsequently, lost by 



