SUPPLEMENTARY NOTE B. 119 



and jointing. I have repeatedly observed the same thing at 

 other places in the neighbourhood of Sunderland; on one 

 occasion a coralloid with a stem as thick as a man's arm, came 

 under my notice. It is also a common occurrence, where semi- 

 globular bodies are developed, for them to be integrally con- 

 nected with the surface-portion (usually upper) of a bed. 



Fig. 2 represents a portion (about a foot square) taken from 

 a bed at Building Hill. The oblique lines represent west-of- 

 north joints, and the horizontal bounding lines bedding-planes, 

 The specimen, with several others of the kind, was collected 

 about the year 1839, on an occasion when the quarrymen had 

 exposed a singularly beautiful development of such forms. In 

 this example, as in the section fig. 1, the coralloids branch off 

 from the planes of bedding and jointing ; but one of its features 

 is worth special notice : the coralloids, according to a note I 

 made at the time, are best developed where branching from the 

 west bounding-plane of the meridional joints. These examples 

 are amply sufficient to disprove the idea that they were formed 

 at the same time as that in which the limestone was deposited j 

 also that, howsoever they may have originated, the agent which 

 produced them must have penetrated the partings of both jointing 

 and bedding. It cannot be too strongly impressed on the mind 

 of the reader that the coralloids, also the other configuration to 

 which Dr. Ramsay has referred, are more or less crystalline 

 internally, and consist of carbonate of lime, adding a few per 

 cent, of carbonate of magnesia ; while their matrix, or the body 

 of the rock, is structureless and essentially dolomite. 



