592 THE POPULAR SCIENCE MONTHLY. 



stances carton, oxygen, and calcium made of ? It is trne we call 

 tliem elements or simple substances, meaning by that substances 

 which can not be converted into anything simpler. No matter 

 what influences the so-called elements are subjected to, they can 

 not at present be decomposed. When, therefore, a chemist, after 

 examining any complex substance, is able to say what simple sub- 

 stances are in it, he tells what it is made of. But, I repeat, is his 

 statement final ? Is there nothing more to learn ? Plainly the 

 great questions still remain to be answered : What is an element ? 

 Are the forms of matter which we call elements absolutely inde- 

 pendent of each other, or are they not in turn composed of still 

 subtler forms of matter which we may hope to discover in the 

 future ? 



While it is impossible to answer these questions at present, 

 some discoveries have been made within the past few years which 

 have a direct bearing upon them. It has been shown by a Russian 

 chemist, Mendelejeff, and at the same time by a German, Lothar 

 Meyer, that the elements are related in a very remarkable way, 

 so closely that it is possible to arrange them all in one table, in 

 which they form parts of a general system. The law governing 

 the variations in properties of the elements is known as the jieri- 

 odic law. The limits of this article will not permit any detailed 

 explanation of this remarkable law. The main point that I wish 

 to emphasize is, that these so-called elements are shown to be re- 

 lated to one another, and it seems impossible, in the light of these 

 facts, to believe that they are distinct forms of matter. It seems 

 much more probable that they are in turn composed of subtler ele- 

 ments, and it has been pointed out that all the substances which 

 we now call elements, of which there are about seventy, can be 

 conceived to be made of two fundamental elements combined in 

 different proportions. There does not, however, appear to be any 

 immediate prospect of discovering these fundamental substances, 

 though we can not, of course, tell what a day may bring forth. 

 While the prospect in this direction is not promising, it appears 

 clear that there are other elements of the same order as those now 

 known yet to be discovered. When Mendelejeff first arranged the 

 known elements in his table, he found that the table was not com- 

 plete, and it became necessary to leave certain places vacant in 

 order to secure a perfectly systematic arrangement. It was as if 

 an incomplete skeleton of some great animal were found. On put- 

 ting the parts together, the finder would discover that something 

 is wanting to complete the whole, but nevertheless he would recog- 

 nize the relations between the parts before him. He would also 

 be able to tell what the general properties of the missing parts 

 must be. So here, the discoverer of the periodic law recognized 

 that the system was incomplete. He pointed out the gaps, and 



