160 ANNUAL OF SCIENTIFIC DISCOVERY. 



the surface. This would leave the summits of the tube partially 

 empty, and warm water, being drawn up from beneath by capillary 

 attraction, would freeze and elevate the column still higher. After 

 mentioning the various appearances which this theory accounts for, 

 the author applies it to the exudations on plants, the only difference 

 being, that the porous pith furnishes the supply of warm water from 

 the earth, while the wedge-shaped medullary rays secure the mechan- 

 ical conditions necessary for the development of the projectile force in 

 the proper direction. The paper is of considerable length, and abounds 

 in interesting details not to be compressed into a short abstract. 



ACTION OF WAVES. 



IN the course of a paper read before the Society of Arts on " artifi- 

 cial breakwaters," by Mr. A. G. Findley, we find some interesting 

 facts concerning the force and action of the waves of the ocean. The 

 dynamic force exerted by sea-waves is greatest at the crest of the wave 

 before it breaks, and its power in raising itself is measured by various 

 facts. At Wasberg, in Norway, in 1820, it rose 400 feet, and on the 

 coast of Cornwall, in 18-13, 300 feet. The author cites numerous other 

 cases, showing that the waves have sometimes raised a column of water 

 equivalent to a pressure of from three to five tons to the square foot. 

 He also proved by a table that the velocity of the waves depends on 

 thoir length, that waves of from 300 to 400 feet in length from crest 

 to crest travel with a velocity of 20 to 27k miles an hour, and this, 

 whether they are 5 or 54 feet in total height. Waves travel very 

 great distances, and are often raised by distant hurricanes, having been 

 felt simultaneously at St. Helena and Ascension, though 600 miles 

 apart, and it is probable that ground swells often originate at the Cape 

 of Good Hope, 3,000 miles distant. Nor do waves exert their force at 

 or near the surface only, one instance being mentioned where a diving- 

 bell at the depth of eight fathoms was moved five feet laterally in calm 

 weather. The motion of " shingle ' : depends on the direction in 

 which the surf strikes the shore, which is influenced by the direction 

 of the wind, and this is shown from observations on the French coast 

 to be in the ratio of 229 days from western quarters to 132 days from 

 eastern quarters. At the British Association, Mr. Stevenson made a 

 statement of the result of certain observations made by him on the 

 force of waves with reference to the construction of marine works. 

 The result of the experiments made gives a force of about li tons per 

 square foot for the German Ocean, and of 3 tons for the Atlantic Ocean. 

 The experiments from which these results were obtained were made at 

 the Bell Rock and Skerryvore light-houses. 



THE ATLANTIC WAVES. 



AT the meeting of the British Association at Edinburgh, Dr. Scores- 

 by read an interesting paper on " the Atlantic waves, their magnitude, 

 velocity, and phenomena," containing the result of observations made 

 during two passages across the Atlantic in 1817-48. The most in- 



