Sept. 1st, 1887.] 



SCIENTIFIC NEWS. 



153 



manure may to a great extent cover the cost of treating the 

 sewage. It will not, however, yield a handsome profit over 

 and above such cost. 



Hence, if there were no necessity for the treatment of 

 sewage, if polluted rivers were not injurious to health, and 

 if their waters could be used without injury in the arts and 

 manufactures, then we should say that sewage-irrigation 

 farming, and in like manner the manufacture of manure by 

 precipitation processes, were poor, very poor investments. 

 But as we are compelled to purify the sewage, the only prac- 

 tical question is. Shall we adopt those methods which yield 

 no return whatever, or rather methods by which we may 

 be, in part at least, recouped for the expense incurred ? 



A JUBILEE RETROSPECT. 



■Xl/E commend the following extracts from the Times' 

 "Jubilee Retrospect." to all who have not already 

 seen it : — 



The keynote of the Victorian era is the development of 

 scientific research, the concomitant growth of practical inven- 

 tion, and the expansion of industry which these have brought 

 about. Other ages have been fruitful of profound scientific 

 conceptions, or have been illustrated by great inventions 

 and discoveries ; but it would be difficult to point to any half- 

 century in the history of the world in which equal progress 

 in speculative science has been combined with anything 

 approaching to the magnitude, variety, and importance, of 

 the applications of science to practical ends which distinguish 

 the present reign. It is as true to-day as at any former period 

 that nothing great can be done in pure science save by men 

 who make the discovery of truth the sole aim of their efforts 

 and who prize no other reward. But it is no less true that 

 abstract and applied science go hand in hand as they never 

 did before, and that each owns enormous obligations to the 

 other. For if the triumphs of the workshop have been 

 achieved by means of the discoveries made in the laboratory, 

 on the other hand the laboratory depends for every step 

 of its advance upon the technical skill and hitherto un- 

 rivalled precision of the workshop. Physical science has 

 reached a stage at which the verification of its hypotheses 

 and the supply of new data for its speculations demand appli- 

 ances of extraordinary excellence, and in many cases a colla- 

 tion of experience and experiment which nothing but 

 the practical inventions of the age could render possible. 

 It is doubtless to the co-ordination of the two forms 

 of intellectual activity that we owe the rapidity of 

 recent advance. An unprecedentedly large army of enquirers 

 has simultaneously pushed the interrogation of nature in a 

 thousand directions, and has attained unprecedented results. 

 But beside them has been working an army larger, and 

 equally keen, of men eagerly seeking to utilise for 

 practical ends every crumb of available information, and 

 giving to scientific ideas a concrete application which often 

 forms the starting-point for new processes of scientific 

 induction. 



The fundamental conceptions of the material universe 

 entertained by educated men have been revolutionised 

 during the last fifty years. The simple atomic theory of 

 the older chemistry has given place to a molecular theory, 

 which itself has undergone considerable development. The 

 outlines of the elements which the older chemistry accepted 

 as an ultimate analysis are melting under the gaze of the 

 spectroscopist, who across the haze of their wavering 

 figures catches glimpses of a simple primal matter. The 

 evolution of matter is, however, like the evolution of living 

 forms, a philosophical conception which must always rest 



rather upon the general necessities of thought than upon 

 actual experiment. The immutability of certain forms of 

 matter in all the conditions that we can devise or have any 

 experience of is as absolute as the persistence of specific 

 types in the animal or vegetable kingdom. The most refrac- 

 tory substances have been vapouriscd in the electric arc, and 

 the most attenuated gases have assumed the solid form under 

 the combined influence of intense cold and enormous pres- 

 sure. But we have made no nearer approach to actual evi- 

 dence, either of material evolution or of the complexity of 

 the so-called elements, than may be inferred from certain 

 spectroscopic observations of the sun, and some experiments 

 tending to show that in some cases we have confounded two 

 or more very similar elements under one name. Apart, how- 

 ever, from these abstruse speculations, the whole tendency 

 of physical and chem'cal investigation has been to bridge 

 the gulf formerly fixed between molar and molecular motion 

 and between chemical and mechanical force. There is an 

 obvious interdependence between this scientific movement 

 and the doctrine of the cnservation of energy, which is one 

 of the main philosophical achievements of the epoch under 

 discussion. According to that doctrine, the total energy cf 

 any body or system of bodies is a quantity as absolutely fixed, 

 and as incapable of suftering either increase or diminution, as 

 the matter of which these bodies are composed. Energy, 

 like matter, may assume an endless variety of forms ; but 

 the force put forth by the locomotive is as indestructible as 

 the particles which compose its framework or its fuel. But 

 to balance our account we have to take cognisance, not only 

 of the forces of impact or pressure of which we have direct 

 experience, and conceive ourselves to have tolerably full 

 understanding, but also of the forces of attraction and repu'.- 

 sion in their various forms, concerning which we as yet 

 know absolutely nothing beyond the fact of their existence 

 as inferred from their effects. To refer the whole complex 

 sum of these energies to a general law, and to deal with 

 them on fundamental physical and mathematical principles 

 is the aim of the physical science of to-day. Notwithstanding 

 all superficial resemblances, it stands difterentiated from the 

 science of all past ages, by the clearness with which it appre- 

 hends the nature of this quest, and the unrivalled range of 

 the analytical methods it has brought to bear. In the domain 

 of biology the theory of evolution first placed upon a scientific 

 basis by the genius of Darwin, is a product of the same great 

 movement of philosophic thought which brought forth the 

 molecular theory of matter, and the doctrine of the conserva- 

 tion of energy. The idea of evolution itself was not new ; 

 but what was new was the proof that in the vast geological 

 changes establishei by the labours of Lyell and other 

 workers in the same field, in the visible tendency to varia- 

 tions in existing plants and animals, and in the evidence, 

 collected by Darwin's industry and observation, of the power 

 of the struggle for existence to exercise, in given conditions, 

 a selective and protective influence upon occasional varia- 

 tions, we have all the data required for the construction of a 

 coherent theory. Evolution has now definitely taken its 

 place as a working scientific hypothesis, not, indeed, capable 

 of explaming all the facts of biology, but consistent with 

 these facts, and furnishing — the most that a scientific 

 hypothesis can ever do — the means of systematising our 

 knowledge in preparation for a further advance. The 

 study of embryology is already modifying profoundly the 

 interpretation put upon the evolutionary theory, and is pro- 

 bably paving the way for some new generalisation. Mr. 

 Herbert Spencer's application of the theory of evolution to 

 the facts of social order is the expression, in the sphere 01 

 human thought and action, of the intellectual movement ot 

 which Darwin made himself the exponent in the field of 

 biology. 



