50 PROCURING OBJECTS. 



sand and dust, shaken out of the West Indian sponges into the bins 

 or casks in which they are kept by dealers, be swept up and examined, 

 it will be found to abound in minute shells, corals, and other interesting 

 remains of marine animals ; and among them many species of forami- 

 nifera are found, which appear very closely allied to many of the 

 same family that I have seen in the fossil state. Species of echini, 

 spicula of sponges, and an infinite variety of minute organic remains 

 will reward the researches of the observer. The sponges themselves, 

 in the state in which they are imported, are also well worthy of the 

 trouble of a careful examination, especially those parts that are usually 

 trimmed from the base, as being too full of impurities to be sold ; many 

 very beautitul specimens are thus found attached to the fibres of the 

 sponge. I have not found many organic remains in the sand shaken 

 out of the Turkey sponges ; but it is probable that if the sand from 

 such sponges, obtained from other localities, were to be carefully 

 looked over, new and interesting objects would be the result of such 

 an investigation." 



49. SHELLS IN CHALK. Many, and probably all, white chalk rocks 

 are the produce of microscopic coral animalcules, which are mostly 

 quite invisible to the naked eye, possessing calcareous shells, of which 

 more than one million are well preserved in each cubic inch, that is, 

 much more than ten millions in one pound of chalk. The extreme 

 minuteness of the chalk animalcules is strikingly proved by this, that 

 even in the finest levigated whiting, multitudes of them are still pre- 

 sent, and may be applied, without suffering change, to the most varied 

 technical purposes; thus, in the chalk coating given to painted cham- 

 bers, paper, or even glazed visiting cards (when not coated with white 

 lead alone) may be seen a pretty mosaic of well-preserved moss-coral 

 animalcules, but which are invisible to the naked eye; and thus our 

 natural vision receives from such a surface the impression of the purest 

 white, little dreaming that it contains the bodies of millions of self- 

 existing beings of varied and beautiful forms, more or less closely 

 crowded together. 



The best method of examining into the animalcular composition of 

 chalk, is that recommended by Ehrenberg,* which is as follows: 



* Ann. Natural History, June, 1841, p. 309. 



