6 Dana — American Journal of Science, 1818-1918. 



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. 



In geology, vast progress has been made in the 

 knowledge of the earth, not only as to its features now 

 exhibited at or near the surface, but also as to its history 

 in past ages, of the development of its structure, the 

 minute history of its life, the phenomena of its earth- 

 quakes, volcanoes, etc. Geological surveys in all civilized 

 countries have been carried to a high degree of per- 

 fection. 



In biology, itself a word which though used by 

 Lamarck did not come into use till taken up by Huxley, 

 and then by Herbert Spencer in the middle of the cen- 

 tury, the progress is no less remarkable as is well devel- 

 oped in a later chapter of this number. 



