THE GROWTH OF SCIENCE IN THE NINETEENTH CENTURY. 175 



Again and again we may read in the words of some man of old the 

 outlines of an idea which in later days has shone forth as a great 

 acknowledged truth. From the mouth of the man of old the idea 

 dropped barren, fruitless; the world was not ready for it, and heeded 

 it not; the concomitant and abutting truths which could give it power 

 to work were wanting. Coming back again in later daj's, the same 

 idea found the world awaiting it; things were in travail preparing for 

 it, and some one, seizing the right moment to put it forth again, leaped 

 into fame. It is not so much the men of science who make science as 

 some spirit which, born of the truths already won, drives the man of 

 science onward and uses him to win new truths in turn. 



It is because each man of science is not his own master, but one of 

 many obedient servants of an impulse which was at work long before 

 him, and will work long after him, that in science there is no falling 

 back. In respect to other things there may be times of darkness and 

 times of light; there may be risings, decadences, and revivals. In sci- 

 ence there is only progress. The path may not be always a straight 

 line; there may ])e swerving to this side and to that; ideas may seem to 

 return again and again to the same point of the intellectual compass; 

 but it will always be found that they hav<^ reached a higher level — they 

 have moved, not in a circle, but in a spiral. Moreover, science is not 

 fashioned as is a house, by putting brick to brick, that which is once 

 put remaining as it was put to the end. The growth of science is that 

 of a living being. As in the embr3'o, phase follows phase, and each 

 member or body puts on in succession different appearances, though 

 all the while the same member, so a scientilic conception of one age 

 seems to differ from that of a following age, though it is the same one 

 in the process of being made; and as the dim outlines of the early 

 embryo become, as the being grows more distinct and sharp, like a 

 picture on a screen brought more and more into focus, so the dim 

 gropings and searchings of the men of science of old are b}^ repeated 

 approximations wrought into the clear and exact conclusions of later 

 times. 



The story of natural knowledge, of science, in the nineteenth cen- 

 tury, as, indeed, in preceding centuries, is, I repeat, a stoiy of con- 

 tinued progress. There is in it not so much as a hint of falling back, 

 not even of standing still. What is gained by scientific inquiry is 

 gained forever; it may be added to, it ma}^ seem to be covered up, 

 but it can never be taken awa3^ Confident that the progress will go 

 on, we can not help peering into the years to come and straining our 

 eyes to foresee what science will become and what it will do as they 

 roll on. While we do so, the thought must come to us, Will all the 

 increasing knowledge of nature avail only to change the ways of man; 

 will it have no effect on man himself^ 



The material good which mankind has gained and is gaining through 



