224 Dr. J. D. Macdonalcl on Deep-sea Soundings. 



XXVIII. — Examination of Deep-sea Soundings ; zoith Re- 

 marks on the Habit and Structure of the Polycystina. By 

 John Denis Macdonald, M.D., F.R.S., StafF-Surgeon, 

 H.M.S. 'Lord Warden'* 



Vice-Admieal ^ie H. R.YelveetoNj K.C.B., having handed 

 over to me a small bottle of deep-sea soundings, given to him 

 by StafF-Captain Calver, of H.M.S. ' Porcupine/ with a short 

 descriptive paper, I submitted it to microscopic examination, 

 and obtained some interesting results. 



It will be convenient to preface my own observations with 

 a copy of the paper above mentioned. 



Specimen of Soundings. 



" Position .... Lat. 47° 35' N., Long. 12° 15' W. 



" Depth 2435 fathoms (3 statute miles). 



" Temperature . Surface, 65°-5 F. ; bottom, 36°-5 F. 



" Pressure .... 457 atmospheres = 6855 lbs. 



" Time occupied. Sounding, 3 hours. 



„ „ Dredge-sinking, 2 hours. 



„ ,, Dredge-working, 2 hours. 



„ „ Dredge-raising, 4 hours. 



" The above pressure will be more readily understood when it is 

 mentioned that a man of ordinary size would, at the foregoing 

 depth, be subjected to a pressure equal to the weight of thirty 

 goods trains loaded with pig-iron, with their engines and tenders 

 included ; and yet creatures of great beauty and dehcacy hve, move, 

 and have their being in this vast depth. 



" The specimen consists of tine calcareous mud with myriads of 

 Globigeringe and other Foraminifera." 



It is quite true that " fine calcareous mud, with myriads of 

 Globigerinse and other Foraminifera" exist in the soundings 

 in question ; but on treating them with boiling nitric acid, a 

 large amount of siliceous particles and mineral grit, intermixed 

 with interesting Polycystina and Diatomacese, were brought 

 into view after the destruction of the carbonate of lime. 



List of Genera observed. 



Diatomacece. Polycystina. 



Cosciuodiscus. Astromma. 



Actiuoptyclius. Poclocyrtis. 



Gallionella. Eucyrtidium. 



Sui'irella. Stylodictya. 



Synedra. Dictyocha. 



Navicula. Lj-clinocamum. 



* Communicated by the Director General of the Medical Department 

 of the Navv. 



