AND OTHER WATER WAVES 71 



relation between the size of waves and the size 

 of the basin in which they were formed, I used 

 either observed lengths, or lengths calculated from 

 the period, according to which were available, I 

 find that in observations from shipboard in the 

 open ocean there is in this matter a troublesome 

 discrepancy. Most of the " wave-lengths " given 

 in published records such as those of Scoresby 

 and Paris were not really observed as an apparent 

 distance separating two ridges of water viewed 

 simultaneously, but are deduced by calculation from 

 observed speeds. The speed is obtained in the 

 way described by Dr. Scoresby, viz., the observa- 

 tion of the time taken by a wave -crest to run the 

 length of the ship, combined with the interval be- 

 tween the arrival of two wave -crests, the speed 

 of the ship being known. When the ship is broad- 

 side on to the waves their apparent period should 

 enable one to calculate at once the wave-length. 

 I found, however, when observing at sea, that the 

 length so calculated was much greater than the 

 apparent distance between successive convexities 

 of the water's surface. I have also found that many 

 officers on the Atlantic liners disclaim ever having 

 witnessed in the North Atlantic waves of the great 

 lengths which are measured indirectly by system- 

 atic observers from the observed speeds of, and 



