18 A CENTURY OF SCIENCE 



the imagination has been realized, and man has gained 

 the conquest of the air ; while the perfection of the sub- 

 marine is as wonderful as its work can be deadly. 



Hardly less marvelous is the practical annihilation of 

 space and time in the electric transmission of human 

 thought and speech by wire and by ether waves. While, 

 still further, the same electrical current now gives man 

 his artificial illumination and serves him in a thousand 

 ways besides. 



But the limitations of space have also been conquered, 

 during the same period, by the spectroscope which brings 

 a knowledge of the material nature of the sun and the 

 fixed stars and of their motion in the line of sight ; while 

 spectrum analysis has revealed the existence of many 

 new elements and opened up vistas as to the nature of 

 matter. 



The chemist and the physicist, often working together 

 in the investigation of the problems lying between their 

 two departments, have accumulated a staggering array 

 of new facts from which the principles of their sciences 

 have been deduced. Many new elements have been dis- 

 covered, in fact nearly all called for by the periodic law ; 

 the so-called fixed gases have been liquefied, and now air 

 in liquid form is almost a plaything; the absolute zero 

 has been nearly reached in the boiling point of helium; 

 physical measurements in great precision have been car- 

 ried out in both directions for temperatures far beyond 

 any scale that was early conceived possible; the atom, 

 once supposed to be indivisible, has been shown to be made 

 up of the much smaller electrons, while its disintegration 

 in radium and its derivatives has been traced out and 

 with consequences only as yet partly understood but cer- 

 tainly having far-reaching consequences; at one point 

 we seem to be brought near to the transmutation of the 

 elements which was so long the dream of the alchemist. 

 Still again photography has been discovered and per- 

 fected and with the use of X-rays it gives a picture of the 

 structure of bodies totally opaque to the eye ; the same 

 X-rays seem likely to locate and determine the atoms in 

 the crystal. 



Here and at many other points we are reaching out to 

 a knowledge of the ultimate nature of matter. 



