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NATURAL SCIENCE. November, 



block to split. The best way, then, is either to moisten the blocks 

 before immersion, or to let them stand in a shallow layer of water 

 b)efore filling up the bowl. Blocks which are cracked, or in which 

 there are obvious marly veins traversing the chalk, should be wrapped 

 in muslin lightly tied round with string before being immersed, and 

 very damaged or precious specimens had better be moistened by 

 means of a spray-producer before they receive their bath. Another 

 good plan is to build a strengthening wall of plaster of Paris around 

 the broken parts of a block. If one collects Bryozoa, and has some five 

 hundred specimens as the result of a tour, it will be found that a daily 

 changing of water becomes a weariness to the flesh. This may be 

 readily and cheaply obviated by making a platform by means of half- 

 inch wire-netting strained over a stout wire ring ; and the apparatus is 

 made more perfect by the addition of a couple of stout wire handles 

 and four short wire supports to act as feet. The platform is made of 

 such a size that it closely fits the sides of a large pan, near to the 

 bottom, on which the feet alone rest. All debris then falls clear of the 

 blocks, and settles at the bottom of the vessel. In this way fifty small 

 blocks can be changed in as many seconds. These suggestions for 

 soaking the blocks apply to all beds in the Upper and Middle Chalk. 

 But with the Grey Chalk and Chalk-marl it is different, as, in the 

 first place, the salt does not show up so plainly when the specimen is 

 dry, and in the second, the combination of clay and lime does not 

 readily lend itself to permeation by water. The Chalk-marl is the 

 worse of the two, and with the exception of the large echinoderms, it is 

 better to avoid the process, as in many instances the matrix melts 

 away in the water. And the same, in varying degree, applies to the 

 Grey Chalk, though the Belemnitella plena marl, and certain bands in 

 the zone of Ammonites rhotomagensis stand the immersion well. 

 Specimens of Salenia and Pseudodiadema, if spineless, can readily be 

 taken out of the matrix, and they then offer a good resistance to the 

 water. 



In passing, one may mention that Gault fossils are best worked 

 with a knife when they are slightly moist, and that beautiful results 

 may be obtained by using a badger-hair brush. Fossils from the 

 Thanet Sands, if tide- washed, are very difficult to preserve, as the salt 

 simply splits them to pieces. If the block of friable sandstone is 

 trimmed, and the edges and base well dabbed with a strong solution of 

 silicate of potash, one can sometimes successfully soak them ; but to 

 do this one must spray them first, and then lower them into shallow 

 water on a glass plate fitted with wire handles. These Tertiary sands 

 are so friable that it is often impossible to carry home a specimen of 

 any size, and in such cases it is a good plan to trench out the specimen 

 with a knife, coat the sides of the square or oblong with silicate, in situ, 

 come back in an hour's time, and remove it from the cliff. 



Should Chalk fossils be worked with a wet or with a dry brush ? 

 Clearly, with the exception of the large echinoids and the more 



