THE RARE EARTHS. MAGEE. Ixxv 



limits for their size and weight, while Mcndelejeff and Meyer have 

 propounded a theory of classification. The subtle points will yet be 

 chained and their properties scrutinized. 



For a long time, ever since chemistry became a science in fact, the 

 need of a proper method of classification has been felt. There was no 

 order, no opportunity therefore to apply mathematics, there was no compre- 

 hensive and easy means of grasping the subject, each element and almost 

 every compound must be studied by itself. So greatly was the need 

 felt that, whenever a new property common to a lew or several elements 

 was noticed, attempts were made to make it the basis of a classification. 

 Berzelius thought he had discovered a method but this was soon found 

 wanting, not being founded on sufficient data ; when Faraday discovered 

 the relations of the elements to the poles of the electric battery it was sup- 

 posed to be settled, but this soon showed itself as a common property for 

 all, extending from one end of the list of elements to the other and giving 

 no special point where it could be said one class ended and another 

 began, it soon resolved itself into the older metals and non-metals, 

 basigens and acidigens and so failed, it was founded on the too narrow 

 basis of a single property. Inklings of the truth were, however, 

 obtained from time to time. Dobereiner seems to have made the first 

 suggestion which has led to the present system. He classified many of 

 the elements into triads,' taking as a basis a property certainly common 

 to all, viz, weight. He first noted that in many cases the weight of one 

 element was the mean of that of two others usually resembling it, secondly, 

 in other cases three elements with very similar properties possess very 

 nearly equal atomic weights, viz, Li., Na., K., and S., Se., Te., for 

 examples of the first and Fe., Co., Ni., and El, Rh., Pd., as examples of 

 the second. The comparisons were continued by Pettenkofer, Dumas 

 and others, clearer and still clearer signs of universal order appearing 

 as the atomic weights were more and more accurately calculated. 

 Newlands was able between 1860 and 1866 to arrange the elements in 

 octads, but the gaps were so many and the table so fragmentary, and 

 moreover so many elements were forced to stand aside that his friends 

 jocularly suggested that he try arranging the elements according to the 

 first letters of their names. Had Newlands possessed the full courage 

 of his convictions England would have received the credit of the greatest 

 advance in Chemistry since Liebig and Wohler founded Organic Chemis- 

 try. It was left, however, for bolder minds. Lothar Meyer, and 



