EDITORIAL NOTES. 



This volume contains Parts IV., V., VI., and VII. of the Physical and 

 Chemical series of Reports on the Scientific Results of the Expedition. 



Part IV. — While conducting the experimental work connected with the 

 behaviour of the Challenger thermometers under pressure, a Report on which 

 forms Appendix A to Volume II. of the Narrative of the Cruise, a number of 

 subsidiary experiments of great interest, more or less connected with Ocean 

 Physics, were suggested and partly carried out by Professor Tait. These 

 and cognate matters were more fully investigated subsequently, and formed 

 the basis of the present Report by Professor Tait "On some of the 

 Physical Properties of Fresh and Sea Water." This title by no means 

 indicates the variety of the subjects treated of experimentally and otherwise ; 

 for instance, the compression of glass, salt solutions, and mercury are 

 investigated, and a discussion is given of the curious question (raised by 

 Laplace's researches) of the internal pressure of a liquid mass, and historical 

 details on these subjects are recorded. An examination of the Report will 

 show the great amount of experimental and other work that was necessary 

 for the production of this most valuable paper. 



The Report occupies 76 pages of letterpress, illustrated by 2 plates. 



Part V. — Previous to the departure of the Challenger Expedition in 

 1872, discussions of the more fundamental problems of meteorology relative 

 to the diurnal changes in atmospheric pressure, temperature, humidity, 

 and wind, were almost exclusively restricted to observations made on 

 land. It had then, however, become evident that data supplied exclu- 

 sively by observations on land, which occupies little more than a fourth 

 part of the earth's surface, were altogether inadequate to a right con- 



