106 GENEEAL HISTOEY OF THE INFUSOEIA. 



Coddington lens can easily detect the larger Diatoms as they are precipitated. 

 In about a quarter of an hour, many of the larger forms will have descended 

 to the bottom of the tube. By turning the tap at the bottom of the tube, I 

 let out a di'op of the mixture on a slide, and examine it Tvdth a low power 

 (i-inch) ; and if it be tolerably clear, and the Diatoms of one character, I then 

 let off five or six inches of the mixture into a test-tube, and set it aside for 

 re -examination after the Diatoms have subsided. In a quarter of an hour 

 more, I again let off into another test-tube six or eight inches more of the 

 mixture, and place it aside to settle. In half an hour more I let off into 

 another test-tube six or eight inches of the mixtm^e, which will contain the 

 finer Diatoms by themselves, generally free from all mud and sand. I then 

 pass each of these washings again through the long tube of distilled water ; 

 and by examining the mixture during the process of its subsidence, I am 

 enabled to let out the heavier particles of sand or mud, and to obtain pretty 

 clean all those Diatoms which are alike in size, or at all events in specific 

 gravity. Some Diatoms take a longer time than others in settling to the 

 bottom of the tube, and separating themselves from extraneous matter, such 

 as the Nitzschia, CJosteriwn, &c. ; but, by a little patience, and an extra 

 washing through the tube, these difficulties may, in a great measure, be 

 overcome. By this method, I have found the Pleurosigmata, P'lnnularice, 

 Surirellce, and Synedrce very well separated, those of a like character being 

 found together. I have been stimulated to send these few remarks on the 

 washing of Diatomacese, on account of the great difficulty I have hitherto 

 experienced in procuiing slides free from mud, sand, and other extraneous 

 matters." 



Mr. Okeden offers the following plan for obtaining specimens imbedded in 

 mud at considerable depths, in making borings for engineering purposes. He 

 prefaces the description of his apparatus by that of the usual boring ap- 

 paratus, which ^' consists essentially of any number of iron rods " (J. M. S. 

 1854, p. 2Q), "which screw one into the other ; to one of these is screwed an 

 auger or a chisel-point, as the case may requii'e. This is inserted into the 

 groimd to be tested, and worked round by manual force and downward pres- 

 sure, length after length of rod being added as the ground is penetrated. In 

 addition, then, to this apparatus, I obtained, fii'st, several lengths of wrought- 

 iron gas-pipe, about an inch in diameter, and each screwing into the other ; 

 and also a similar number of iron rods, each a few inches longer than the 

 lengths of gas-piping, and each also screwing into the other : to the end of 

 one of these lengths of rod is attached a cork of the exact diameter of the 

 gas-pipe, or a trifle larger. This cork is fixed by a washer and nut. The 

 gas-piping should be in lengths of about 8 feet each, as this is the most con- 

 venient in work : one of these lengths should also be again divided into two 

 parts, which must, however, screw and unscrew ; and this length is to be 

 the one first put into the ground or mud, for reasons which I will presently 

 explain. 



" The mode of proceeding is as follows : First, a hole is bored to the requii'cd 

 depth — say 20 feet — mth the usual boring apparatus ; this done, the appa- 

 ratus is di^awn out, the jointed length of gas-pipe is now introduced, — the end 

 of it, with the rod to which the cork is attached, having been previously 

 stopped, the rod passing up the centre of the gas-pipe ; this is let down the 

 hole, another length of pipe being attached, and another length of rod, and 

 so on, length after length of pipe and rod, until the bottom of the hole is 

 reached. We shall thus have a continuous length of gas-piping, which wiU 

 be penetrated by a continuous length of iron rod attached to the cork at the 

 end of the pipe. It is obvious that this cork will entirely prevent any foreign 



