ABSTRACT OF PROCEEDINGS. xliii. 



disposal was very small. Neither has it yet been obtained in a 

 crystallized condition ; its best solvent appears to be glacial acetic 

 acid, to which it imparts a rich blue colour. It appears to be 

 quite distinct from indigo, also from the blue pigment of lobster 

 shell and other blue substances, the colour of the Emu egg shell 

 seems to be somewhat similar. Its ash contains a good deal of 

 iron, phosphoric oxide, lime and some magnesia. Rather more 

 than 1% of the crude pigment was obtained from a freshly col- 

 lected specimen, an old waterworn dead specimen yielded only 

 •26% of pigment. It does not readily lend itself to dyeing either 

 silk, wool, or cotton. On extracting it in a percolator with 

 glacial acetic acid or with absolute alcohol it after a time changes 

 to a green colour. Dilute solutions of indigo in acetic acid or of 

 sulphindigolic acid fade much more quickly than solutions of the 

 coral blue of equal depths of colour. 



EXHIBITS. 



1. Mr. Hamlet exhibited a small spectroscope by Reichert. It 

 consisted of a system of direct vision prisms, a reflecting prism by 

 means of which a separate spectrum may be observed at the same 

 time j a bright-line micrometer scale enables the observer to locate 

 at once the right position of absorption bands or the usual lines 

 emitted by incandescent bodies. He also shewed a convenient 

 Abbe refractometer by Reichert of Vienna, for ascertaining the 

 refractive indices of oils and other liquid substances. The prin- 

 ciple of construction of the instrument is based on total reflection, 

 which takes place at a thin film of liquid enclosed between two 

 prisms of high refractive power. To use the instrument, one of 

 the prisms is removed and the exposed surface of the other brought 

 into the horizontal plane. A drop of liquid is then placed on it 

 and covered by the second prism. An adjustment is made to the 

 boundary between light and dark. Dispersion is removed by a 

 compensator, and the index of refraction is read off directly from 

 the scale. 



2. Prof. David exhibited, on behalf of Mr. E. C. Andrews, b.a., 

 specimens collected by the latter from the raised coral reefs of the 



