SCIENCE-GOSSIP. 



323 



from the Triassic beds of the Midland counties. 

 The evidence obtained from an examination of the 

 manganiferous beds would seem to show that the 

 oxide of manganese was transported in a similar 

 way. Amongst some of the beds in one of the 

 gravel-pits near Watford I found a block of 

 quartzite which enclosed between the walls of 

 a very narrow fissure a quantity of manganiferous 

 powder ; this powder was black, and resembled that 

 found in the beds. In the " Geology of the Warwick- 

 shire Coal-field," one of the memoirs of the Geological 

 Survey, it is stated that at Tuttle Hill, near 

 Nuneaton, the quartzite contains oxide of man- 

 ganese in joints and fissures of the rock, and that 

 at one time the quartzite was worked for the 

 oxide of manganese which it contained. The 



quartzite in which the manganese occurred in the 

 Watford gravel-pit was similar to the quartzite 

 found near Nuneaton. Lumps of oxide of 

 manganese, weighing from one to sixty pounds 

 each, are found in the New Red Marl near 

 Nuneaton, and have been profitably worked. 

 Such lumps may have been the source of some 

 portions of the manganiferous beds of Hertfordshire. 

 From the above facts, it may be reasonably 

 inferred that some of the quartzite and other 

 blocks found in the glacial drift of some parts of 

 Hertfordshire were transported, together with 

 oxide of manganese, from the Nuneaton district, 

 and were afterwards re-arranged and re-deposited 

 by the action of water in motion. 



Rokeby Lodge, St. Alban's Road, Watford, Herts. 



COLLECTING DESMIDS. 

 By R. Williamson. 



■nPHE following hints result from the experience 

 of several years' practice in gathering 

 desmids. It is astonishing what a large number 

 of forms will often be found in places which may 

 have been passed many times without detecting 

 them. The best places to procure desmids are 

 small pools on open moors, on peaty ground ; 

 pools which are exposed to sun and rain. Next, 

 are freshwater lochs, lakes, ponds and ditches ; in 

 fact, they may be found almost anywhere where 

 water collects without becom- 

 ing stagnant. 



In many cases desmids may 

 be seen with the unaided eye 

 as minute green specks in the 

 water, but in the majority they 

 will have to be looked for 

 with a pocket-lens, and later 

 under the microscope at home. 



Having indicated v;here to 

 find the desmids, I will now 

 proceed to point out the best 

 way of collecting them. First 

 provide yourself with a number 

 of test-tube bottles having flat 

 bottoms, and fitted with corks. 

 In size, three-quarters of 

 an inch by three inches long is very suitable. 

 The most convenient way to carry the specimens 

 is to get an ordinary elastic cricket-belt and 

 fasten on to it a piece of cloth, linen or canvas, 

 which has been folded and stitched up in such a 

 way as to leave pockets the correct size for the 

 tubes to slip into tightly. In fact the whole arrange- 

 ment, when finished, bears a strong resemblance 

 to an ordinary cartridge-belt. In this way twenty 

 or more tubes may be carried clasped round the 



Fig. I. — Straining-Net for Desmids. 



waist and under the coat away from observation. 

 It is a system also convenient for taking out a 

 tube with wet fingers and replacing when filled. 



In order that one may with some reasonable 

 certainty expect to find such small objects in such 

 a quantity of water recourse must be had to 

 straining the water on the spot. This is easily 

 done by means of a muslin conical funnel with a 

 bottle attached to a wire ring fixed to the end of 

 a walking-stick. (See fig. i.) 



A suitable size is one having 

 a ring six inches in diameter, 

 made of quarter-inch round 

 wire. The muslin cone is 

 stitched to the ring. The 

 small end of the cone is left 

 open about two inches in 

 diameter, and tied with string 

 to a two-ounce wide-mouthed 

 bottle. The depth of cone 

 should be about six inches. 



With this instrument the 

 water may be searched by 

 hand, or in the case of small 

 pools it may be filled by 

 means of a small bottle used 

 as a ladle to lift water into 

 the funnel. Of course, the water passes through 

 the muslin funnel, leaving the desmids on the 

 inside. These gradually gravitate into the bottle. 

 When a sufficient quantity has been thus filtered, 

 empty the contents into one of the test tubes. 

 In this way a very rich harvest may be carried 

 home in very small bulk. It is advisable to 

 take samples from pools which may only be 

 separated by a few yards distance, because 

 different types may often thus be found quite close 



