These applications of chemistry have been rendered possible by improved methods of investigation, a greater knowledge of the nature of matter itself, and the perfection of scientific instruments of precision. These instruments are so much finer and more delicate than our senses that they have been the means of disclosing the actual constitution of matter. A man might sit and “meditate” upon the nature of matter for years, but he would be no nearer an actual _proof_ as to its constitution than he was at the beginning. It is generally conceded that Aristotle possessed one of the finest minds the world has ever known; yet any school boy today knows more of the ultimate constitution of matter than did Aristotle. The reason for this is that instrumental methods of research have enabled us to see and measure the ultimate properties of matter,--which our unaided senses would never permit us to do. The development of science in other fields, therefore, has rendered possible the rapid growth of chemistry, during the past century; and chemistry, in turn, has assisted the other sciences. Thus does all knowledge work hand in hand, when co-operation is rendered possible! SALINITY OF THE OCEANS I referred some time ago to the calculations which had been made as to the age of the earth, based upon researches as to the salinity of the ocean. As we know, the water of all the oceans is salt water; only that of rivers and lakes is “fresh.” But the degree of the ocean’s saltness is not quite constant. It varies, since evaporation is constantly taking place; sediments are deposited; and above all vast quantities of water are being poured into the ocean by the hundreds of rivers which flow into it, carrying all kinds of earthy deposits which have been washed away by their passage through the river-beds over which they flow.