382 POPULAR LECTURES AND ADDRESSES. 



the water is expelled as the air expands when the 

 tube is brought to the surface. 



My navigational sounding machine was brought 

 into practical use for the first time in the steamship 

 Palm, belonging to Messrs. Charles Horsfall & Co., 

 Liverpool, in a voyage to Odessa and back about a 

 year ago, in command of Captain E. Leighton. I 

 cannot illustrate the use of the machine better than 

 by reading to you an extract from a letter I received 

 last April from Captain Leighton, describing his 

 experience of it in this first trial : 



" During the voyage in the Palm steamship, 

 which has just come to an end, I took frequent oppor- 

 tunities of testing the sounding machine when I had a 

 chance of cross-bearings to verify the depths as 

 shown by chart, and always found it most accurate. 

 For instance, going up through the Archipelago and 

 just after clearingthe Zea Channel, I got a good posi- 

 tion by bearings, chart showing 79 and 76 fathoms, 

 two casts of your glass gave 78 and 75 fathoms. 

 In the Bosphorus also it gave capital results in 

 30 to 40 fathoms water. 



"The first real use I made of the machine was in 

 the Black Sea during a fog which obscured every- 

 thing. Wishing to make sure of my position I 

 put the ship's head for the land, and kept the 

 machine at work. After running in to 30 fathoms 

 at full speed I slowed down and went in to 12 

 fathoms, then hauled out to a convenient depth 

 and put her on the course up the coast. When it 



