418 Notices of Memoirs — Castracane on Diatomacece 



accidentally be discovered upon the surface of granite., or any other 

 older rock, without any one assuming that they grew in the period 

 of the granite's formation. 



Such objections did actually occur to my mind ; they lost all force, 

 however, by the reflection that the scrap of coal upon which my 

 examination had been made oame out of the solid mass of that 

 mineral, and not from off the surface ; besides, the piece from which 

 it was detached is preserved in the Mineralogical Cabinet of the 

 " Sapienza " in Koine, and thus the discovery made by me may be 

 controverted by other people at any time. 



These examinations are rendered easy to me from the special 

 arrangement of my microscope, which is such that it enables me to 

 be sure of having examined in turn each point of the entire substance, 

 giving me, besides, leisure to mark the position of the smallest form 

 whatsoever, in order to be able to find it again at any moment. 

 After having fully determined the fact of the presence of Diatoms 

 in the Liverpool coal, I resolved to ascertain whether the same could 

 be detected in coal from other sources. With this intention I have 

 up to the present time made analogous investigations upon three 

 other samples obtained from the before-mentioned Mineralogical 

 Cabinet. One is from the mines of St.-Etienne, another came from 

 Newcastle, and the third was a fragment of the so-called " cannel- 

 coal " of Scotland. Not a single one of these different substances 

 failed to reveal Diatoms in greater or less numbers. Of these I 

 did not remark any that were not fresh- water; nevertheless the 

 species varied in each. The forms I found did not give me occasion 

 to note any novelty whatsoever, while there was not one among 

 them of which I would have hesitated in declaring that it was a living 

 form. Thus the presence of Diatoms (which seemed to me such a 

 great fact to have been able to prove in the Liverpool coal) showed 

 itself persistently in the three other different kinds, so that I begin 

 to suspect that perhaps Diatoms accompany every stratum of coal. 



From the presence of Diatoms in coals not only does the principle 

 established by me of the necessity of Diatoms in water to maintain 

 animal life stand confirmed, but we have a new subject of study in 

 recognizing the highly important part which Diatoms and microscopic 

 life have ever played upon the earth. 



From all this arises the necessity of the geologist directing the 

 greatest attention to whatever traces remain to us of these minute 

 beings which had so much share in the history of the globe. 



I am encouraged to hope that these observations of mine, or at 

 least the fact proved by me of the presence of Diatoms in coal, 

 will not be regarded as undeserving attention by some geologist or 

 micrographer. It will be most gratifying to me if my remarks and 

 experiments, under the direction of some more competent person, 

 prove any advantage to science. In that case, in order to facilitate 

 the task still more to any one less expert who may wish to under- 

 take such an examination, I shall add a hint as to the process 

 followed by me in conducting these researches. The course to pursue 

 is decided by the flinty nature of the Diatom-valves, and in order 



