APPENDIX. 



713 



81. Astreca, Wakes Island. 



32. Astnea, Wakes Island. 



33. Astreca, Feejees. 



34. Astrnsa, Feejees. 



35. Astraa, Feejees. 



36. Shell ofChama. 



" Nine of the above species, of which there was the largest quantity on hand, were 

 selected for a minute determination of each ingredient, while of the others, only the pro- 

 portion of carbonate of lime and animal matter to the other ingredients, was determined. 

 The following are the nine selected : 



I. Porites favosa (No. 1), Sandwich Islands. 

 II. Madrepora palmatum (No. 9), West Indies. 



III. Madrepora spicifera (No. 10), Ceylon. 



IV. Madrepora prolifera (No. 11), Bermudas. 

 V. Madrepora plantaginea (No. 12), Ceylon. 



VI. Pocillopora ligulata (No. 22), Sandwich Islands. 



VII. Meandrina phrygia (No. 28), Ceylon. 



VIII. Astrtea orion (No. 29), Ceylon. 



IX. Asirrca (No. 30, p. 721, pi. 13, fig. 15). 



" A few remarks are added upon some of their physical characters, before giving the 

 mode and results of analysis. 



" Hardness. All the various corals examined were superior in ha'rdness to calcareous 

 spar or common marble, and not inferior to Arragonite ; while some were as hard as 

 Apatite or crystallized phosphate of lime ; or according to the scale used by mineralo- 

 gists, the usual hardness will be expressed by 4, though in a few instances as high as 5. 

 Using an iron mortar in the earlier trials, the iron pestle was roughened and cut under 

 the resistance of the angular masses of coral, to a degree quite remarkable considering 

 the nature of the substance operated on. So much iron was communicated to the powder 

 from this source, that recourse was had to a mortar of porcelain, and even this was not 

 proof against wear, the porcelain pestle being pitted by the repeated blows. The more 

 porous species, of course, were crushed with less difficulty ; and this was especially the 

 case with the species of Porites. 



" Specific Gravity. The specimens were reduced to fine powder before trying the spe- 

 cific gravity, as the porous character of the coral would otherwise interfere with obtaining 

 correct results. Considerable variation will be observed in the following table. The 

 numbers correspond to the catalogue on the preceding page. 



179 



