General Introduction 



so much as the generations have swept along, 

 there has been a parallel advance in knowledge 

 at work, and a parallel alliance there of near and 

 remote. As the web of science is unfolded the 

 more closely do we find its threads knit together. 



At the beginning of the nineteenth century 

 certain salts of silver were found sensitive to light, 

 and photography was born. In its latest em- 

 ployment it has reproduced books; seized every 

 detail of a bird's flight; enabled the rainbow to 

 paint its every hue; depicted stars and nebulae 

 far beyond telescopic vision; caught the shadow 

 of a bullet buried in human bones. Progress in 

 photography is no more than abreast of progress 

 in chemistry, electricity, engineering. Every 

 discovery of a cardinal fact or law extends the 

 range of applied science with a bound, and with 

 a bound which ever lengthens. For each fact 

 and law has a vital tie with every other, and adds 

 one to the multiplier enriching thought and life; 

 when the capital of science increases, so also 

 does the rate of interest at which it compounds. 



In its material and immediate sphere, we are 

 in little danger of forgetting the rapid growth of 

 the wealth of science. We are daily informed of 

 some fresh marvel of ingenuity in railroad ap- 

 pliance, in the creations of naval and engineering 

 architecture. Every newspaper tells us of some 

 new piece of scientific ingenuity electric, tele- 

 scopic, chemic all intended to enlarge human 

 powers, or to confer upon man powers wholly 

 new. Remarkable as all these practical applica- 

 vii 



