440 ' PHILOSOPHICAL TRANSACTIONS. [aNNO 1773. 



softer than marble, but harder than alabaster, and which therefore Mr. K. calls 

 a species of marble. 



The water, that flowed into the pit on all sides, issued from a stratum of 

 hard brown and reddish sand-stone, replete with shining sparry micae, and some 

 ocherous matter; and had, in its passage through the trunk, regularly filled up 

 the cavity by slow degrees, with solid incrustations; so that the increase of the 

 marble is marked much in the same manner as the increase of the growth of a 

 tree appears to be, when its trunk is cut horizontally: and at last the water had 

 left only a cavity, which appears in the middle of the block, and which was 

 uniform in its figure from one end of the pipe to the other, and nearly similar 

 to the original cavity; but which, at last, not being large enough to let all the 

 water pass, occasioned the discovery. Since that time, in order to prevent the 

 inconvenience, if possible, a new trunk has been made, larger than the first; 

 and yet, in June 1771? this new trunk also was so far filled up with the sparry 

 incrustation, that there was but just room to thrust 4 fingers into the central 

 cavity; and the lateral shoots, or troughs, also have filled so fast, that they have 

 been obliged every now and then to be cleaned out. 



Mr. K. adds the following observations, 1st. As the water flowed in from 

 the shoots, on 2 sides of the square trunk or pipe, it is manifest that the 

 streams must have stricken against each other, at the corner of the pipe where 

 they first met, and also at the opposite corner. And, as it is a known principle 

 of mechanics, that a body, which is acted on by 2 forces, moving in different 

 directions, will describe the diagonal of a parallelogram, of which the directions 

 of those forces is the sides; so here, the line in which the two streams met, and 

 impeded each other's motions, has plainly, as the marble increased, gone on in 

 the diagonal of such a parallelogram from both the corners, viz. from that where 

 the pipe joined the shoots, or troughs, and from the opposite one; but it is also 

 very remarkable, that there is such a diagonal line, not only at these corners, 

 but in like manner at the other two; which can be accounted for no otherwise, 

 than by supposing that each of the 2 streams, dashing against the opposite side 

 of the pipe, formed continually, the whole way down, another stream, in a 

 contrary direction; and so, both together, produced the same effect throughout 

 the whole pipe, as if there had been 4 streams flowing over the 4 sides. On 

 examining the block however, very strictly, it appears, that the lines in the dia- 

 gonal one way, are stronger than those in the diagonal the other way ; and indeed 

 the specimen of the pipe, presented to the Society, has even broken in halves, 

 exactly in one of the diagonals, though the block here described remains entire, 

 and has the appearance of having had its sides joined accurately, in the manner 

 in which a skilful workman would fit 4 boards to be glued together. 



2dly. At one place there seems to have been, by some accident or other, the 



