176 



THE MUSEUM. 



join in a lake, the uniting currents 

 form a reflexive, wave-like current 

 which sets back towards the headland 

 which separated the streams. This 

 current gradually ceases, from lack of 

 propulsive power, and deposits a sedi- 

 ment, particles of sand and silt which 

 the water held in suspension when in 

 more rapid motion. This is invariably 

 the case and if the head-land is near 

 enough the silt will be deposited upon 

 it, forming a sand-bar which, in time 

 will become a fertile meadow. The 

 action of the waves in beating against 

 it and returning as an under-tow will 

 cause the sides to assume a nearly per- 

 pendicular position. If the head-land 

 is too far from the angle of the uniting 

 streams for the revlexine current to 

 reach with its burden, the silt will be 

 deposited upon the bed of the lake and 

 there form a conical shaped hill. 

 Owing to the waves, such hills seldom 

 reach the surface. 



Now, if the theory that the lake 

 once existed, the surface of which 

 coincided with the upper series of 

 wave lines, be true, we shall find a de- 

 posit of silt in the angle of its currents; 

 and if the theory that the lake was 

 suddenly chained, as by the bursting 

 of the barrier, be true we shall find 

 that the sides will be as nearly per- 

 pendicular as the material of which the 

 deposit is composed will admit, but if 

 the lake was drained gradually, then 

 the sides of the deposit will have a cor- 

 respondingly gradual slope. 



Let us then see to what extent the 

 facts support the theory. In the east- 

 ern part of the city, joining the head- 

 land and extending towards the junc- 

 tion of the two streams and exactly 

 where we should naturally expect to 



Trochus niloticus. Pearl Trocius, China, Sin- 

 gapore. A beautiful Banded species, but 

 most frequently seen in polished 

 state, as per cut. 



find it, is a perfectly flat plateau, com- 

 posed entirely of silt. Moreover its 

 elevation corresponds with the height 

 of the upper series of wave lines. 

 Thus the first part of the theory is sus- 

 tained. The sides of this hill, which 

 by the way is locally known as Semin- 

 ary Hill and upon which are located 

 the Methodist Seminary, the United 

 States Arsenal and many private resi- 

 dences are so steep that it is only by a 

 long circuitous route, or by an expen- 

 sive system of grading that the plateau 

 can be reached by teams. In places 

 it appears as though large portions of 

 earth near the edge o) the plateau had 

 loosened and slid down ttie steep side 

 of the hill. The cohesion of the par- 

 ticles of earth was not sufficient to sus- 

 tain the entire deposit in places when 

 the water was withdrawn. The ori- 

 ginal surface has been changed by cul- 

 tivation and by grading, but still its 

 whole appearance corroborates the 

 second part of the theory. 



TO BE CONTINUED. 



