20 



KNOWLEDGE. 



[January, 1902. 



sand than is possible with the glass or metal slip usually 

 rocomnicndcd for use. 



Thus equipped, the collector sallies forth between the 

 tides. Probably everyone has noticed when at the scar 

 sido the white lines which nin along the sands, parallel 

 with the retreating tide. A pocket lens shows that the 

 white material consists of the minute shells of 

 Foraminifera, of which some arc of a lustrous white 

 colour, duo to the comparative abundance of the 

 Miliolida: — a family of common occurrence in shore 

 gatherings, characterised by opaque shells of a milky 

 white or " Porce/lanous " texture, while others ai-e more 

 or less glassy and transparent. These " Hyaline " forms are 

 much less noticeable to the naked eye. They are mixed 

 in vai-ying proportions with fragments of shell substance, 

 Ostracode shells, cinders and the lighter drhris of the 

 shore, and their presence in these lines is duo to the 

 separating action of the water, which on a smaller scale 

 we shall later on employ in the cleaning of our collected 

 material. The rocking action of the wave on the 

 extreme edge of the ebbing tide keeps these shells and 

 fragments of light specific gravity in suspension until 

 after the heavier sand grains have subsided, and so they 

 are left behind in the ripple marks and depressions of 

 the sand. Sometimes a local eddy of the tide, produced 

 by the neighbourhood of a projecting rock, or of groynes 

 and piere, causes the material to be gathered together in 

 largo quantities, which show as extensive white patches 

 on the sand, and prove a real gold mine to the collector, 

 who will then obtain more material in half an hour than 

 he could gather in several days from the ripple marks. 



The collector must not conclude that there are no 

 Foraminifera present because there are no white patches 

 to bo seen, but remembering the way in which these 

 patches are fomied of the lighter debris of the shore, 

 must look for Foraminifera wherever he obsei-ves that 

 such debris has been deposited. 



On every coast, at intervals of varying distance, there 

 are spots which appear to be the foci of the local tides 

 and currents, and here the material will be found in 

 the gi-eatest abundance. These points will soon be 

 discovered and may be worked at every tide ; but they 

 vai'y continually with the set of the tide and wind, so 

 that a spot which has proved rich may be quite bai'e 

 the next year. Thus in October, 1896, I found Bognor — 

 always a rich collecting gi'ound — had its richest point to 

 the west of the pier; while in September, 1901, there 

 was very little material obtainable except at Felpham, 

 two miles to the east, where the beach was thick with 

 debris. 



Having found the material the collection is quite an 

 easy matter. With the celluloid scraper at an angle of 

 about 60° the thin surface film of Foraminifera and 

 debris is easily scraped into a heap and transferred to 

 the box or bag. Great cai-e must be exercised not to 

 dig down into the sand, for nothing but a heavy bag 

 will result from this, the Foraminifera being confined 

 to the surface layer. The material thus collected may 

 bo either cleaned at once, or after being slowly dried — 

 avoiding great heat — may be packed away in bottles for 

 a more convenient period. 



The apparatus required for the cleaning and prepara- 

 tion of the dried material is simple and inexpensive, 

 and, if desired, much of it may be easily improvised. 

 The most necessary articles are a photographic develop- 

 ing dish of china, quarter or half plate size, according 

 to fancy, sieves of difi'ercnt sizes and materials according 

 to the collector's pocket, a cylindrical glass jar with a 

 lip and without any neck or constriction at the top. 



and a retort stand or tripod made of an iron ring 

 rivotted on three logs. 



The sieves can be made by any copper-smith, and it 

 is very convenient to have a series of varying degrees 

 of coarseness; but for the beginner two sieves of 40 

 and 120 meshes to the inch respectively will be sufficient. 

 My own sieves are of copper, 4 inches high, 4 inches 

 diameter at top, sloping to 3 inches diameter at the 

 bottom. A smaller size made of telescope tubing H 

 inches in diameter and 1 inch deep is very useful for 

 washing small gatherings. Zinc, which is cheaper than 

 copper, can be used for the sieves. 



The wire gauze, which can be obtained from any 

 large ironmonger, vaines in price according to the 

 number of meshes to the inch, ranging from a few 

 pence per square foot to four shillings for the finest 

 obtainable, which has 120 meshes to the inch, the 

 diameter of each aperture being about jJ-^ inch. If a 

 finer sieve than this is required, as it sometimes may 

 be, the size of the aperture may be reduced by silver- 

 plating the gauze, or preferably by the use of silk bolting 

 cloth, which may be obtained up to 200 meshes to the 

 inch. The wire gauze must be strained tightly over 

 the sieve and soldered neatly to the edge, so that there 

 is no ledge of solder inside to retain unwashed material. 

 If silk is iised, a sieve must be made without a bottom 

 and having a tui'ued-back edge at the lower end, so that 

 the silk may be strained across and secured with string 

 or a rubber band. The most useful sizes for a series 

 of sieves are, in my opinion, 12, 20, 40, 80, 120 and 

 ] 50 (silk) meshes to the inch. 



Before cleaning the material it must be slowly and 

 thoroughly dried. It should then be passed through 

 the 12-mesh sieve to remove all the coarse debris, stopes, 

 shells, cinders, etc. None of the British shore species 

 except parasitic fomis will be found in this coarse 

 residuum, but it should be looked over with a pocket 

 lens for these or for abnormally large specimens. In 

 some dredged materials and in tropical gatherings, how- 

 ever, this coarse residiuim will be found to be full of 

 Foraminifera. 



The material which has passed through the 12-mesh 

 sieve consists of Foraminifera mixed with other light 

 debris and a considerable quantity of sand, and the 

 collector must now proceed to eliminate the whole, or 

 nearly the whole, of the sand and as much as possible 

 of the other debris by means of two operations, " float- 

 ing " and " rocking." If the quantity of material to 

 be operated upon is small, it may be treated off-hand, 

 but if there is much, it is well to sift it out into vaiying 

 degrees of fineness, by passing it through a series of 

 sieves. This will simplify the floating operations by 

 ensuring that the particles are approximately of 

 similar weight. 



The floating operations must be performed at a sink, 

 and, if possible, in daylight, the process being more 

 uncertain by artificial light. The finest sieve (120 wire 

 or 150 silk) is thoroughly wetted and rested on tho 

 ti-ipod. The glass jar is then filled with water nearlv 

 to the brim, and a few spoonfuls of sand slowly poured 

 into it. If the material is coarse the sand sinks instantly, 

 and in tlie course of a few seconds most of the Forar 

 minifera follow suit. By holding the jar to the light 

 the course of the falling particles can be followed, and 

 at the proper moment a sudden tilt empties the whole 

 of the water and most of the Foraminifera into the 

 sieve, the sand and a few of the heaviest " Forams " being 

 left in the jar. The purity of the material in the sieve, 

 which is usually called " floatings," will depend upon 



