M. Ehrenberg's Observations on Microscopic Organisms. 387 



year 1840 suggested the idea to M. Hagen to make similar 

 experiments upon the deposits at Pillau, and to communicate 

 his observations. The specimens of the deposits which he 

 transmitted to M. Ehrenberg are still richer in organized be- 

 ings than those of Wismar. They often constitute, according 

 to the result of forty experiments made upon different samples, 

 one fourth, and sometimes even a half of the entire volume. 

 Hence it will follow, that at Pillau also there is annually se- 

 parated from the running waters from 7200 to 14,400 cubic 

 metres of pure microscopic organisms, which, in the course of 

 a century, would supply, in this place alone, a deposit of from 

 720,000 to 1,140,000 cubic metres of infusory rock or tripoli 

 stone. 



Both at Wismar and Pillau there is to be met with in the 

 organized materials, some forms which are entirely. new, and 

 others which belong to the waters of the ocean. As it regards 

 the best harbour, which is in the channel called Pillau-Hafe, 

 the north wind often causes the sea-water to flow into the 

 river. 



M. Ehrenberg also alludes to the researches he made con- 

 cerning the muds of the river Elbe at Cuxhaven, and which 

 were submitted to the attention of the Berlin Academy in the 

 year 1839. These muds also appeared to be composed, to 

 the extent of nearly half their volume, partly of Infusoria with 

 siliceous heads, and partly of Polythalames with calcareous 

 heads. 



To these observations M. Ehrenberg now adds the results 

 of his recent observations upon the mud of the Nile, the de- 

 posit of which has, from the remotest period, attracted the at- 

 tention of the curious. He has purposely compared with 

 this mud, African deposits procured from Daebbe and Ambu- 

 kohl, in Dongola, — from Tangcur, in Nubia, — from Thebes 

 and Gyzeh, in Upper Egypt, — from Boulak, near Cahira, — 

 and from Damietta, in Lower Egypt. He has also in his pos- 

 session specimens of the ancient deposits of the Nile, which 

 M. Parthey and Lieutenant- General Minutoli brought to Ber- 

 lin. In all these specimens, he has found that the Sponges, 

 the Siliceous Infusoria, and, especially from the neighbourhood 

 of Damietta, the calcareous Polythalames of the arable districts 



