414 Dr. G. J. Stone)' on the 



Author to his scientific friends, with the permission of the 

 Secretaries of the Royal Society. 



" 2. The curve of the diagram is the Logarithmic Spiral 

 described in a memoir that is referred to in the heading to 

 the diagram. 



" Observation. — Another spiral, nearly coincident with 

 that of the figure, may be derived from an elliptic law. The 

 Logarithmic Law appears the more probable, but for the 

 present use of chemists it is immaterial whether the curve 

 be derived from the logarithmic or the elliptic law. What 

 they are chiefly interested in are the properties enumerated 

 below, which, with the exception of the amount of the devia- 

 tions, are common to both curves. 



u 3. The cardinal feature of the diagram is that it repre- 

 sents atomic weights by volumes, not by lines. 



u The volume of the globe in the centre represents the 

 atomic weight of hydrogen. 



" The atomic weights of the other elements, are represented 

 on the same scale by the volumes of concentric spheres ex- 

 tending out to the points intended to be indicated by the 

 symbols of the elements. 



" 4. These points lie along the radii, and so near to their 

 intersections with Ihe logarithmic spiral that they are within 

 a millimetre of that curve in fifty-nine instances. Such de- 

 viations are too small to be conveniently represented on the 

 diagram ; but the deviations of the other six elements — 

 H, Li, Ca, Fe, Te, W — are indicated. The deviations of 

 these six elements on the scaJe of the figure amount respec- 

 tively to 4-2-92, -1-32, -1-51, -1-08, +1*00, -P14 

 ' millimetres/ 



[The original of Plate IV. being of inconvenient size has 

 been reduced in about the ratio of 8 to 9. Accordingly, 

 the values of the maximum deviations given above are too 

 large, and require to be diminished in that ratio to reduce 

 them to the same scale as Plate IV.] 



" 5. The deviations (of which the foregoing are the largest) 

 follow definite laws which are in part investigated in the 

 memoir. The dotted spiral and the little curved lines of the 

 figure have reference to these laws. 



" 6. The atomic sphere of hydrogen is drawn upon the 

 diagram, and the others are so easily conceived, that the 

 diagram represents the atomic weights in a form which the 

 mind can effectually grasp. 



" This is the chief peculiarity of the diagram. 



" 7. The quadrants are alternately electro-positive and 

 electro-negative. The transition between these states is 

 gradual elsewhere, but becomes abrupt between sesqui-radins 



