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



XXVIII. — Examination of Deep-sea Houndings ; with Pie- 

 marks on the Habit and Structure of the Polycystina. By 

 John Dexis Macdonald, M.D., F.R.S., Staff-Siirgeon, 

 H.M.S. ' Lord Warden '*. 



Vice-Admiral Sir H.R.Yelverton, K.C.B., having handed 

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

 by Stafi-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 Sound'mgs. 



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



" Depth 2435 fathoms (3 statute miles). 



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



''Pressure .... 457 atmospheres = Gb55 lbs. 



" Time occupied. Sounding, 3 hours. 



„ „ Dredge-sinking, 2 hours. 



„ „ Dredge-working, 2 hours. 



„ „ Dredge-raising, 4 hours. 



" The above ju'essure "will be more readily undei-stood 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 delicacy hve, move, 

 and have their being in this vast depth. 



" The specimen consists of hue calcareous mud with myriads of 

 Globigerina; and other Poraminifera." 



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

 Globigerinffi 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 

 Avith interesting Polycystina and Diatomacea^, were brought 

 into view after the destruction of the carbonate of lime. 



List of Genera observed. 



Diafoinaced'. Poli/ci/sd'na. 



("oscinodiscus. Astronnna. 



Actiiidptychus. Podoiyrtis. 



( iallioneUa. Kucyrtidium. 



Smirclla. Stylodictya. 



Sy lU'dra. 1 )ictyoohu. 



iVnvicula. Lychuocamuni. 



* ("oiuuuiuicatiHl by the I)iit(tiir (uncial i>f the Medical Pepartuieiit 

 of the Navv. 



