738 REPORT — 1900. 



features Althougli descrioed by Professor Sedgwick more than sixty years ago 

 with other magnesian beds in the north of England, it is still comparatively 

 unknown. He divided the concretions in these strata into ten classes, but I have 

 been unable to Hnd any classified collection except the one in the Newcastle 

 Mineum ; even this is only partially done 



My own studies at Fulwell and Hendon lead me to suggest a new classification, 

 with^^ye primary forms,_ viz. (1) rods, (2) bands, Qi) rings, (4) balls and modified 

 spheres, (5) eggs. Combinations of these forms constitute the major part of these 

 massive beds, and frequently a bed of less than a foot thick shows examples of 

 several different corabinatio'iis. These I place in ten classes, though they may have 

 to be added to. The chief types are (1) tubes, (2) ' caulifiowers,' {?>) basaltiform, 

 (4) irregular, (5 and 6) troughs and bands (two kinds), (7) ' fanlike,' (8 and 9) 

 'honeycomb' or coralloid (two kinds"), (10) pseudo-organic. 



Photographs were exhibited on the screen showing both the primary forms and 

 the combinations as seen (wherever possible) in the undisturbed rock sections. 



My ovyn conclusions are as follows : 



1. That the rod structure is secondary to the formation of the conspicuous 

 bands which run across the beds at various angles. (These bands need to be 

 distinguished from the bands mentioned amoug the ' primary forms ') The 

 conspicuous bands act as planes of origin for the ' rods,' and do not cross through 

 the long axes of the rods themselves. They appear never to cross the bedding 

 planes,"though occasionally they follow them and also the outhne of the joints. 

 The question therefore arises, whether this does not give us a clue to the age 

 and sequence of the changes which have occurred in these beds, and whether the 

 previous existence of joints does not mean that the beds were already above the 

 sea-level when the changes commenced. 



2. The rods invariably start from the last-mentioned bands, and may be seen 

 at every possible angle. As they have grown upwards and obliquely as well as 

 downwards, the term ' stalactitic ' is a very misleading one to use. As Mr. 

 Garwood stated long ago, these beds 'present many points which appear irrecon- 

 cilable with the theory of their stalactitic origin.' 



3. The first step in the series of changes which have taken place was probably 

 an orderly but unsymmetrical arrangement of amorphous molecules of calcium 

 carbonate which separated themselves from those of the carbonate of magnesia. 



4. The internal architecture is due to such arrangement of amorphous particles 

 of lime which has since been coated with an outer crystalline layer. In some cases, 

 however, the central part has undergone a complete subsequent change into a 

 crystalline condition. 



5 Pearl-spar (crystals of the combined carbonates) is not always met with. I 

 failed to find any. 



6. In the Fulwell beds there are very few fossils, and where met with, as at 

 Marsden, concretionary action is not always traceable near them. 



7. The specimens at Fulwell which arouse the most interest are coralloid 

 masses ('honeycomb' of the quarrymen). They are confined, so far as I could 

 discover, to a stratum, about li foot thick, above the marl bed, and lie in close 

 juxtaposition to each other, which accounts for their peculiar external shape. 



8. Very little evidence of erosion of lime is to be seen anywhere ; unless we may 

 attribute the cavities in the bulls and elsewhere to this cause. 



In conclusion I would point out the close resemblance which exists _ between 

 the ' lines ' and ' planes ' in these concretionary beds, and the ' lines ' which shoot 

 across congealing water. In some respects the architecture of the magnesian beds 

 compares with the ice decorations seen on our window-panes in frosty wea.ther. 



10. Tlie Pebbles of the Hollybush Conglomerate, and their bearing on Lower 

 and Cambrian Palceogeography. By Theodore Groom, M.A., D.Sc. 



The Malvern Hills are commonly supposed to have formed part of an old coast 

 during the deposition of the Lower Palseozoic bed£._ A preliminary eiamiijation 



