4 o THE POPULAR SCIENCE MONTHLY. 



now passed away. To the writings of Aristotle, who lived during 

 the fourth century B. c., are credited the first bathymetric data. 

 He states that the Black Sea has whirlpools so deep that the lead 

 has never reached the bottom ; that the Black Sea is deeper than 

 the Sea of Azov, that the .^Egean is deeper than the Black Sea, 

 and that the Tyrrhenian and Sardinian Seas are deeper than all 

 the others. The first record of a deep-sea sounding should be 

 credited to Posidonius, who stated, about a century B. c., that the 

 sea about Sardinia had been sounded to a depth of one thousand 

 fathoms. No account is given of the manner in which the sound- 

 ing was taken, and we have no information as to the methods 

 employed by the ancients in these bathymetric measurements. 



The opinions of the learned with respect to the greatest depth 

 of the sea, in the first and second centuries A. D., may be gleaned 

 from the writings of Plutarch and Cleomedes, the first of whom 

 says, " The geometers think that no mountain exceeds ten stadia 

 [about one geographic mile] in height, and no sea ten stadia in 

 depth." And the second : " Those who doubt the sphericity of the 

 earth on account of the hollows of the sea and the elevation of 

 the mountains, are mistaken. There does not, in fact, exist a 

 mountain higher than fifteen stadia, and that is also the depth of 

 the ocean." 



There was no important addition to our knowledge of the deep 

 sea during the middle ages, and no definite attempt to provide 

 effective means for deep-sea sounding appears to have been made 

 until Mcolaus Causanus, who lived in the first half of the fifteenth 

 century, invented an apparatus consisting of a hollow sphere, to 

 which a weight was attached by means of a hook, intended to 

 carry the sphere down through the water with a certain velocity. 

 On touching the ground the weight became detached and the 

 sphere ascended alone. The depth was calculated from the time 

 the sphere was under water. This apparatus was afterward mod- 

 ified by Pliicher and Alberti, and, in the seventeenth century, by 

 Hooke, who substituted a piece of light wood well varnished over 

 for the hollow sphere. Hooke's instrument was no doubt fairly 

 accurate in shallow water, but useless in great depths, where the 

 enormous pressure waterlogged the wood and, by materially in- 

 creasing its density, greatly diminished the speed with which it 

 rose from the bottom. When used in currents the float was car- 

 ried away and the record lost. 



During the period when the voyages of Columbus, Vasco da 

 Gama, and Magellan added a hemisphere to the chart of the world 

 and forever established the fundamental principles of all scientific 

 geography, navigators had sounding lines of one hundred and two 

 hundred fathoms in length, and, although they eagerly studied the 

 oceanic phenomena revealed at the surface, the deep sea did not 





