132 IRRANGI^MENT OP THE SEDtMGKT OP WATER. 



fccea furmed ; a museum not confined to any one particular 

 branch, but comprehending alike the three great depart- 

 ments of nature, the zoological, botanical, and mineral 

 productions of the island, upon the grandest scale possible. 

 It will not be too much to say, that this museum, from the 

 science evinced in its arrangement, independent of its im- 

 portance as a collection of choice and valuable specimens, 

 must, to those desirous of such knowledge, prove a most 

 instructive school ; and afford an inexhaustible fund of In- 

 formation to all those, who think the Natural Flistory of their 

 own country worth attending to, 

 1 am, SIR, 



Your most obedient servant, 

 Mr. Nicholson. JAMES PARKINSON, 



SepU Gth, 1807. Hoxtiyji Square, 



Author of *' Organic Remains,'* 

 ** Memoranda Chemica,'* &c. 



XI. 



Inquiry respecting a Fact not hitherto noticed in the way of 

 discussion^ In a Letter from R. B. 



To. Mr. NICHOLSON. 

 SIR, 



Sediment of V V HEN turbid water has become clear by subsidence, 



water thrown ^^ light stratum of earthy matter, which covers the bottom 

 jato undula- ° . •^ i • • i 



tion arranges of the vessel, is often, as might be expected, distributed 



rr' yr ^^^^^' without any particular appearance of, symmetry : but if 

 the vessel be slightly moved liorizontally, so as to produce 

 an undulation of the fluid, without much disturbing the 

 deposit, this matter is found to arrange itself in a num- 

 ber of parallel ridges or embankments; or at least to indi- 

 cate a manifest tendency to form such ridges. I tind a 



Whj? great difficulty in accounting for this fact. It seems to 



suppose alternate differences in the velocity of the water, 

 as it runs over the bottom. These, however, seem incom- 

 patible with the almost .total want of elasticity in water. 



Perhaps 



