SECTIONAL TRANSACTIONS.— C. 351 



as large, solid incrustations are liable to crack up when merely supported on a 

 flexible film. 



I have found that a modification, combining the essential processes of both methods, 

 is of great assistance when one cannot tell whether the preparation is to be kept 

 uncovered or not. This enables one to convert a preparation of the uncovered type 

 into one of the covered, more permanent, type without much difficulty. The advantage 

 of keeping a preparation uncovered is that features of relief are almost entirely lost 

 when the surface is covered with balsam. 



Dr. W. F. Whittard. — Method of Study of the Detailed Structure of 

 Graptolites Preserved in Calcareous Grits. 



In Harper's Dingle on the south-east flank of the Wrekin (Shropshire), there out- 

 crops a thin band of calcareous grit of Upper Valentian age. In addition to a shelly 

 fauna, characterised by an abundance of Pentamenis oblongus, J. de C. Sow, the grit 

 has yielded numerous specimens of Glyptograptus tamariscus (Nich.) associated with 

 rare Monograptus nudus, Lapw., and M. gemmalus, Barr. The rock consists of angular 

 quartz grains cemented by calcite, the latter occurring in irregular areas which are 

 optically continuous. By treatment with acids, therefore, the graptoUtes may be 

 completely isolated, and the following account details the process employed in the 

 determination of the structure of Olyptograptus tamariscus. 



The grit is trimmed as near the fossil as is deemed safe and then placed in strong 

 hydrochloric acid for a week. Most of the calcareous matter by this time is dissolved, 

 leaving a slightly incoherent mass of quartz grains, which is transferred to a paraffin- 

 wax dish containing commercial hydrofluoric acid. After twenty -four hours the grapto- 

 lite is isolated, then washed and placed for periods of five minutes in successively 

 stronger and stronger mixtures of alcohol and distilled water until it is completely 

 dehydrated. The alcohol is removed by soaking in either clove-oil or xylol, after which 

 treatment the fossil is transferred to celloidin dissolved in clove-oil. A glass plate, 

 about one inch square, is cleaned and covered by a thin layer of paraffin-wax ; the 

 specimen is removed to the plate, covered with celloidin and submerged under 

 chloroform. The celloidin hardens in about one hour, and may be trimmed as much 

 as possible before transference first to xylol and then to paraffin-wax,' which is kept 

 melted in a water-oven. When the celloidin block containing the specimen is thoroughly 

 permeated, it is placed in a dish and covered with paraffin-wax, which, on cooling, 

 completely encloses the celloidin. The wax is then cut into a rectangular block, mounted 

 on a carrier, and fixed in a microtome. The sections, which are obtained in a long 

 ribbon, are permanently mounted on glass slides by the normal microtechnical method. 

 Specimens may be sectioned as thin as 4[x, although lOji. is perhaps a more convenient 

 thickness. 



Wiman's researches on the structuie of the graptolitoidea terminated in 1901, and 

 although he had sectioned many dendroids, he actually microtomed very few diplo- 

 graptids, because he was able to determine their partial structure by clearing the 

 specimens with Schultze's solution. 



Afternoon. 



Excursions to (a) Wolvercote and Kistlington ; (6) Culham^ Abingdon 

 and Radley. 



Saturday, August 7. 



Excursion to Aylesbury, Hartwell, and Wheatley. Luncheon with 

 the Directors of Messrs. Itter's Brick Company, Ltd. 



Sunday, August 8. 



Excursion to Swindon, Faringdon, &c. 



1 Paraffin-wax which melts at 65 deg. is most convenient, but wax with a lower 

 melting-point may be used in a cold room. 



