MODERN SCIENCE. 189 



which J. A. R. NEWLANDS had already foreshadowed (1864) 

 by his Law of Octaves a law in atomic weights which seems 

 to point to the unity of matter, i.e., singleness of one 

 primordial element (perhaps helium, or, according to Crookes, 

 more probably a primal matter which he calls " protyle ") out 

 of which other elements are evolved. Be this as it may, 

 Mendelejeff, investigating Prout's hypothesis (that the weight 

 of a large number of the elements is an exact multiple of 

 that of the hydrogen atoms), found and enunciated his 

 periodic law (1869) : " The properties of the elements are a 

 periodic function of their atomic weights!' From this principle 

 he predicted the existence of several elements required to 

 fill up the gaps in the series of elements, and some of these 

 have since been discovered (Gallium in 1876 one of them), 

 a feat which somewhat resembles that of Leverrier's astro- 

 nomical deductions which led to the discovery of the planet 

 Neptune. 



Such are in the main the results obtained by modern in- 

 vestigators in a field which had been cultivated for thousands 

 of years without bringing in a harvest at all commensurate to 

 the time, labour, ingenuity bestowed upon it. Ancient Egypt, 

 and later, the Arabs, had certainly composed many things 

 dyes, perfumes, poisons, medical remedies, pigments ; they 

 had invented processes of research, and numerous apparatus; 

 they had taught us the value of experiments ; they had 

 founded in Islam, and prepared mediaeval Europe also to 

 found, the Experimental School ; they had even discovered 

 many phenomena, either relating to pure chemistry or pure 

 physics, remarkable and important in an equal degree. But 

 they had failed in one capital point : although they were the 

 first to clearly see and clearly intimate that law governed the 

 world of matter, they had found and formulated no specific 

 chemical laws. The modern era shows no decisive advance 

 in that respect until the XVIIth century. But with Boyle 

 commences the discovery of laws, and from that period, 

 though the progress is by no means rapid until Lavoisier, we 

 witness a continuous development which marks the new times 

 with a new character, and stamps them with a different set of 



