542 " Intelligence and Miscellaneous Articles, 



might hereafter present a seam of coal, which would afford but few 

 distinct traces of palms and forest trees. These phenomena, he says, 

 may explain in part, why so few distinct forms remain of the num- 

 berless forest trees, which must have formed a portion of the vege- 

 table kingdom, at the time of the accumulation of our coal deposits. 



Mr. Hawkshaw does not attempt to explain the process by which 

 dicotyledonous trees are rendered hollow in tropical forests. He 

 expresses doubts respecting the probable nature of the Calamites 

 of the coal measures, and offers no explanation of the means by 

 which they have been preserved in so great abundance. If the coal 

 be considered as the debris of a forest, he says, it is difficult to ac- 

 count for not finding more trunks of trees than have been discovered 

 in our coal basins ; and he observes, it is only perhaps by allowing 

 the original of our coal seams to have been a combination of vege- 

 table matter, analogous to peat, that the difficulty can be solved. 

 In this case, he is of opinion, but a few isolated trees might be ex- 

 pected to be found, and that the remains of vegetable forms most 

 frequently discovered, would only be confirmative of the antiseptic 

 qualities of their original nature, as previously advanced by Professor 

 Lindley, and not of the number or importance of their particular 

 genera at the time of their deposit. 



In conclusion, Mr. Hawkshaw says, that whatever opinion may 

 be drawn from what is conjectural in his paper, it will be obvious, 

 that though fossil remains may be found filled with a mechanical 

 deposit, and containing traces of other vegetables, yet that this con- 

 dition does not prove, that the plants were originally hollow, nor 

 even render it the most likely hypothesis, as they may have been 

 hard wood- trees, the centre of which had been removed by natural 

 processes. 



M. 



LXXVI. Intelligence and Miscellaneous Articles. 



BLUE OXIDE OF TITANIUM. 



KERSTEN has shown that oxide of titanium may be pre- 

 • pared containing less oxygen than titanic acid, and that this 

 blue substance, which has hitherto been prepared only in the moist 

 way, may be obtained in the dry way, and in several modes : 



1st. By passing the vapour of zinc over titanic acid heated to 

 whiteness ; the acid then assumes a dirty blue colour, but loses it, 

 and becomes again white when exposed to oxygen at a high tem- 

 perature. 



2ndly. By putting into a porcelain crucible, metallic zinc, or oxide 

 of zinc mixed with charcoal, and then covering the whole with ti- 

 tanic acid or a titaniferous earthy silicate, and heating the crucible 

 for several hours to whiteness. Fused masses of a lavender blue 

 colour are thus obtained ; they are opake, and contain blue oxide 

 of titanium and oxide of zinc. 



