TWENTY-SEVENTH ANNUAL MEETING. 



101 



According to their specific gravities, thie elements, after the first two 

 octaves, are arranged in hecdecades. In the first two octaves the specific 

 gravities increase in a general way to the middle of each octave, then de- 

 crease to the end. The common difference in the atomic weights of these 

 two octaves is 2. 



After the first two octaves the specific gravity increases somewhat irreg- 

 ularly to the middle of each hecdecade, then decreases similarly to the end. 

 The common difference in atomic weights is 3. Irregularities in atomic 

 weight do not change this mean until the fourth hecdecade, where there 

 seems to be a slight reduction. 



Each hecdecade consists of two full octaves, an accrescent, in which the 

 specific gravities of the several successive elements increase to the end of the 

 octave; and a decrescent, in which the specific gravities regularly fall off from 

 the beginning of the octave to the end. 



The first table contains an additional — a hypothetical — octave, containing 

 the one element hydrogen. Whether this octave shall ever be filled through 

 future discoveries, or by placing therein some of the elements already known 

 and wrongly placed in some other octave, remains to be seen. 



The atomic weights are, unless otherwise specified, as published by Dr. 

 F. W. Clarke, chief chemist U. S. geological survey, January 1, 1894. 



Hydrogen (Hypothetical) Octave. 



* Graphite. 



Between Boron and Carbon is a half-step or minor step ; between Oxj^gen and 

 Fluorine is a step and a half or major step. There is room for an additional ele- 

 ment between O and F; possibly room for elements with C and N. 



Boron and Glucinum seem to differ widely in some respects from the require- 



