AN ATTEMPT TO ILLUSTRATE TIDES AND TIDAL ACTION. 
BY JOHN L. TILTON. 
Plate XVI. 
The inspiration for this paper was due to Professor W. M. Davis, who, 
in an article published in the Journal of School Geography, Vol. 4, No. 7, 
discussed the “Illustration of Tides and Waves”. This led me to think that 
here in an inland town where there is no opportunity for the student 
to observe tidal effects, there is a need for class illustration that I, at 
least, had been neglecting. I consequently drew a plan of what it seemed 
to me would meet the need and employed a local tinner to construct the 
apparatus. The piece proves very satisfactory and seems quite desirable 
not only to illustrate tidal waves in bays of various shapes, but also 
deposition of sediment under various conditions and the formation of 
ripples on sediment. 
The tray is two feet long, one foot wide and five inches deep, the 
partitions three inches high, the entrances to B and E one-half inch 
wide. One end of the tray is occupied by a rectangular pan. A, having a 
handle within it, by means of which the pan may be pressed down into 
water in the tray causing the level of the water to rise; or the pan may 
be raised out of the water causing the level of the water in the tray, to 
fall. B, C, D and E-F represent bays of different shapes; B and E-F, 
large bays with narrow entrances, C a bay narrowing toward its head, 
D an estuary. E-F has two entrances, so that the wave representing 
the tide arrives first through E and later through F. The illustration 
is varied and emphasized by nearly closing the entrance at E with a 
T-shaped piece of tin. The effects may also be further increased by clos- 
ing the wide entrance to C by a piece of tin made to fit around the exposed 
ends of the sides of C. The volume of water that can fiow in near F in 
a few seconds is not large partly because of the narrowness of the pas- 
sage way and partly because of two rounded elevations each about an 
inch high placed six or seven inches apart in the bottom of the passage 
way. 
If a little very fine sand is sprinkled along F and at the entrance 
of the bays the currents are not only rendered more noticeable, but the 
places of erosion and deposition become evident, allowing the student 
opportunity to test his judgment as to the effects, or to observe the ef- 
fects as a basis for further study. In B the sand at ,the entrance is 
swept away by the swift current and spread over the wider parts of the 
bay beyond. Near the entrance of C a bar forms, the outer margin of 
which assumes a slightly crescentic shape. This illustration may be 
( 207 ) 
