J. E. Hilgard—Tidal Waves and Currents. 117 
Art. XVIIIL—On Tidal Waves and Currents along portions of 
the Atlantic Coast of the United States ;* by J. HE. HinGarp, 
Assistant in the Coast Survey, Washington, D. C. 
1. Movement or Tipan WAVEs. 
root of the depth of the sea, may serve as good illustrations of 
the manner in which tides are propagated through sounds, bays 
and rivers. The following table gives the rate of motion for 
different depths : 
Depth in feet___.._- 10 Miles per hour... .--- 12°2 
“ce pA Ree re eens 60 cc ipa Uesieseacpeeigmen 30°0 
“ce a iealubodhes acanaee 100 oe Oe ee 38°7 
ee 1,000 Wee Fe 122°3 
x4 . 6,000 e wo Seas s 299°5 
The movement of the ocean designated by the name of tide- 
wave, does not ebm of the nature of a wave in the common 
will be produced. In the same way the transmission of the 
movement through the incompressible water of the sea, is at- 
tended with 
PS cng from a lecture by Mr. Hilgard before the American Institute, January 
