NATURAL HISTORY SOCIETY OF GLASGOW. 209 



melted layer of common asphalt, free from sand, such as is used 



for street pavements. By this method, as you will see from the 



series of specimens exhibited, I have been successful, beyond my 



expectation, in transferring to the layer of melted asphalt the 



largest fronds of Polyzoa preserved in our shales, in all their 



entirety, and showing the celluliferous face in a manner which is 



hardly excelled in recent sj^ecimens. 



The method adopted may be briefly explained as follows : — 



After selecting the specimens, — it being only those preserved in 



soft shales that can be successfully treated by the asphalt process, 



as those fronds embedded in hard shale or limestone cannot be 



lifted by this method, — let them be well dried at the fire, or in 



the sun's rays, to free them from moisture ; and before applying 



the layer of asphalt, heat the specimens at the fire, this making 



the asphalt adhere much more firmly than when they are cold and 



damp. The asphalt may be melted and spread over the face of 



the frond by a piece of iron, or a kitchen poker, heated nearly to 



redness, having at the same time a bit of tough brown paper 



lying ready to cover the layer of asphalt while it is still warm. 



The paper must be pressed on the asphalt with the fingers, 



and spread smoothly over the surface j and in order that the 



frond may adhere firmly to the asphalt, see that no gum or 



other mucilage is allowed to touch the specimen. The layer of 



paper strengthens the asphalt, and forms a better surface for 



afterwards fixing the specimens to the tablets on which they are 



mounted. For large fronds of Polyzoa, it is better to use two or 



three alternate layers of asj)halt and paper ; which make a 



thin firm cake, not liable to break or crack across when 



being cleaned. Having applied the asphalt, j)lace the shale in 



water, letting it lie for a time. Some shales part from the fronds 



of the Polyzoa in a few minutes, while others will take an hour or 



two, or even a day ; the process may be hastened, however, by 



placing the shale in a saucer filled with water, and as it softens, 



picking it away with the point of a knife, until the face of the 



frond appears. Then w^ash the face of the frond in clean water, 



until the whole of the cell-pores appear quite clean, using a hard 



nail-brush or tooth-brush for the purpose. If the frond has been 



well fixed to the asphalt, it may be washed without fear of 



its removal. When the frond is properly cleaned, the surplus 



asphalt and paper can be cut away from around it by a pair 

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