254 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



results of his long-continued methodical researches on the 

 microscopic life of the sea-bottom of all zones, illustrated by 

 twelve beautiful plates. The second, in 1874, is a resume of 

 the marine microscopic fossils, treated of in the Monatsberichte 

 and Abhandlungen of the Berlin Academy, and in the "Mi- 

 krogeologie." Also an account of the Polycystine formations 

 of Barbadoes and of the Nicobar Islands, illustrated by thirty 

 quarto plates. Following these are remarks on the chalk 

 marble of Antrim and white marl of Lubin, with notes on 

 the fresh-water and volcanic materials yielding Diatomacece, 

 on the economic use of microscopic organisms, and on the 

 systematic classification of Polycystina. To few has it been 

 given to gather together before death their gleanings of 

 knowledge, industriously sought for during the midday of 

 working life, and to harvest their sheaves in such noble vol- 

 umes. 



Dr. Cohen, of Heidelberg, finds that the specks in the Cape 

 diamonds are sometimes due to crystals of specular iron, the 

 larger faces of which lie parallel to the octahedral face of 

 the diamond. 



Dr. Leidy, at a recent meeting of the Philadelphia Acad- 

 emy, stated that the examination of the cut opals from the 

 Queretaro mines, Mexico, shows the brilliant display of colors 

 to be due to reflection from facets one quarter to one milli- 

 meter in breadth of irregular polyhedral forms, a sort of mo- 

 saic pavement on a basis of amorphous opal, but which are 

 distinctly parallel striate, the strire changing in direction on 

 the different facets, so that the whole consists of an aggre- 

 gation of particles, of a striated or finely tubular structure, 

 imbedded in a basis of more amorphous opal, and in polished 

 sections emitting the varied hues for which the precious opal 

 is so much admired, according to the varying fineness of the 

 striae and their inclination. 



