724 



HISTORY OF THE SEA. 



ing upward, so that in the descent the water passes through 

 them freely ; but when it is commenced to haul up, the pres- 

 sure of the water closes the valves. This apparatus is also 

 furnished with weights to sink it, which are release,!, on 



r 



MAMMEV'S 8DUNDINO MACHINE. 



reaching the bottom, by a similar method to those described 

 This instrument was used during the deep sea sounding cruise 

 of the Porcupine, and never once failed. Its faults are its 

 complication, and that it brings up only small samples of the 

 bottom Captair Calver, who used it, could always, v hen at 



