PROGEESS OF MICROSCOPICAL SCIENCE. 249 



25° F., the iustruments became so cold tliat it was unpleasant to 

 handle tliem, and tlic vai^our of the breath condensed and froze at once 

 upon glass and brass-work. Dredging at the considerable depths 

 which we found near the Antarctic Circle became a severe and some- 

 what critical operation, the gear being stiffened and otherwise affected 

 by the cold, and we could not repeat it often, 



" The evening of the 23rd of February was remarkably fine and 

 calm, and it was arranged to dredge on the following morning. The 

 weather changed somewhat during the night, and the wind rose. 

 Captain Nares was, however, most anxious to carry out our object, 

 and the dredge was put over at 5 a.m. We were surrounded by ice- 

 bergs, the wind continued to rise, and a thick snow-storm came on 

 from the south-east. After a time of some anxiety the dredge was got 

 in all right ; but, to our great disappointment, it was empty, — pro- 

 bably the drift of the ship and the motion had prevented its reaching 

 the bottom. In the meantime the wind had risen to a whole gale 

 (force = 10 in the squalls), the thermometer fell to 21°* 5 F., the snow 

 drove in a dry blinding cloud of exquisite star-like crystals, which 

 burned the skin as if they had been red hot, and we were not sorry to 

 be able to retire from the dredging bridge. 



" Careful observations on temperature are already in your hands, 

 reported by Captain Nares. The specific gravity of the water has 

 been taken daily by Mr. Buchanan ; and, during the trip, Mr. Buchanan 

 has determined the amount of carbonic acid in 24 different samples — 

 15 from the surface, 7 from the bottom, and 2 from intermediate 

 depths. The smallest amount of carbonic acid was found in surface- 

 water on the 27th January, near Kerguelen; it amounted to 0"0373 

 gramme per litre. The largest amount, 0'0829 gramme per litre, 

 was found in bottom-water on the 14th February, when close to 

 the Antarctic ice. About the same latitude the amount of car- 

 bonic acid in surface-water rose to the unusual amount of 0*0656 

 gramme per litre ; in all other latitudes it ranged between • 044 and 

 • 054 gramme per litre. From the greater number of these samples 

 the oxygen and nitrogen were extracted, and sealed up in tubes. 



" The considerations connected with the distribution of tempe- 

 rature and specific gravity in these southern waters are so very com- 

 plicated, that I prefer postponing any general resume of the results 

 until there has been time for full consideration. 



" While we were among the ice all possible observations were 

 made on the structure and composition of icebergs. We only regretted 

 greatly that we had no opportunity of watching their birth, or of 

 observing the continuous ice-barrier from which most of them have 

 the ai^pearance of having been detached. The berg- and floe-ice was 

 examined with the microscope, and found to contain the usual Diatoms. 

 Careful drawings of the different forms of icebergs, of the positions 

 which they assume in melting, and of their intimate structure, were 

 made by Mr. Wild, and instantaneous photographs of several were 

 taken from the ship. 



" Upwards of 15,000 observations in meteorology have been 

 recorded duriug the trip to the south. Most of these have already 



