io8 
25 and 26, are specimens of the pale variety of this stone; the 
dark grey and brown varieties may be seen in Case C 35, No. 8, 
and in Case C 38, No. 9. No. 14, in Case C 38, shows dis- 
tinctly the white spots seen in some specimens of Catlinite. 
No. 6, No. 12, and No. 13, in Case C 35, approach Catlinite. 
Other good specimens are No. 5, Case C 34; No. 6, Case 
C 36; and No. 11, in Case C 37. 
er. Chlorite. 
This is an obscure and perhaps rare variety of the mineral known 
as chlorite. But though this stone is apparently a definite mineral 
species, the term chlorite is rather wide, and very careful optical, 
as well as chemical, analysis is needed to refer such specimens 
to their proper place.* The hardness of the particular piece of 
Ohio chlorite (S and D 553) which I have specially studied is 
2*75 ; its density is 2-9. The stone is made up of small lamellar 
crystals, presenting a varied lustre, a pearly aspect, and a pinch- 
beck brown colour. It appears to be accompanied by a trace of 
quartz. The most characteristic specimens of this chlorite in 
the Blackmore Collection are the following : — Case B 33, Tablets 
12, 13; and Case H 4, No. 3. A more ordinary variety of 
chlorite, soft and green, may be seen in Case A 50, Nos. 25 
and 26. 
53. Calcareous Marls and Marly Limestones. 
Some of the pipe materials are characterised by strong 
effervescence with acids. Some of them seem to have been 
made from marls ; that is, natural earthy mixtures of clay and 
calcareous matter. From their composition and softness, they 
would offer less difficulty in manufacture, but would be more 
liable to injury both by moisture and fire than the materials 
already described. They are varied in colour, but are generally 
pale and of earthy aspect, and adherent to the tongue. Some 
are white, some buiT and brown, and some marbled. One 
of the pieces analysed (No. i) was slightly sub-crystalline, but 
usually they are quite amorphous and homogeneous in texture. 
* For the best classification of the species and varieties included under 
chlorite, see Descloiseaux, ' Mineralogie,' tome i. pp. 435 — 483. 
