ON THE ORGANIC STRUCTURE OF FLINT AND OF MEERSCHAUM. 67 



The diagram No. 1 represents a piece of Flint thus stained as 

 seen with a 1-in. obj. glass, when illuminated by means of a 

 parabolic condenser beneath the stage, so as to give a dark back- 

 ground. The upper part of the object being thicker than the 

 lower, the colour is more striking, while the lower part, being thin, 

 the meshes of the net-work are transparent and therefore dark. 

 It is mounted in a dry cell. 



The diagram No. 2 represents the structure of Meerschaum. To 

 render this structure visible requires a little care, for a slice of 

 Meerschaum mounted in Canada balsam is transparent, and in ap- 

 pearance almost structureless. 



The method I have adopted is to take a slice -|-in. thick, to boil 

 it in water to expel the air, and then to boil it in solution of 

 acetate of rosaniline, dry it, saturate it with balsam, harden the 

 balsam by heat, grind one side smooth, fix it on a glass slide with 

 hard balsam, grind it thin, and wash slightly with oil of turpentine. 

 Do not put a glass cover over the object. Illuminate by means of 

 a parabolic condenser beneath the stage, and examine with a 1-in. 

 obj. glass, and you will see what I have depicted. 



This adds o*ne more to the list of nodular bodies, the minute 

 structure of which I have found to have a decidedly organic 

 character. They are as follows : — 



1 . — Meerschaum. 



2. — The Kunkur of the Doab in India. 



3. — The Phosphatic Nodules of the Crag of Suffolk. 



4. — Menilite from Menil-Montant, near Paris. 



5. — Septaria of the London Clay. 



6. — Pace of the Woolwich Beds. 



7.— Flints of the Chalk. 



8. — Iron Pyrites of the Chalk. 



9. — Green-coated Nodules of the Chalk Rock. 

 10. — Phosphatic Nodules of the Cambridge deposit. 

 11. — Phosphatic Nodules of the Gault. 

 12.— The Oolitic Bodies. 

 13. — Ironstone in Coal Measure Sandstones. 

 14.- — Chert of the Mountain Limestone. 



15. — Phosphatic Nodules of the Lower Silurian strata of North 

 Wales. 



As a note to the foregoing remarks, I wish to add, that, by the 



