112 



crement of weight of the body to be sustained. This is shewn to 

 be attained in the case of bare support, when the modulus of the lo- 

 garithmic curve is equal to twice the modulus of cohesion of the 

 substance of which the pendant is composed, in feet. Under these 

 circumstances, the depending mass would be just within the limit of 

 disruption, but its strength would be uniform throughout, and the 

 tendency to separation would at no one point be greater than at ano- 

 ther. It is not imagined that the Gothic architects could have had 

 a mathematical knowledge of a curve, which was not attained till 

 long after, but the degree of tact by which the eye is guided in 

 the selection and adaptation of symmetrical forms seems quite ca- 

 pable of explaining such an approximation to theory, which, it is 

 believed, has not before been noticed. Thus, a depending cylinder 

 appears overloaded at its inferior extremity, a cone towards its 

 middle, and so of all figures which are not concave outwardly. 



2. On the occurrence of the Megalichthys Hibberti in a bed 

 of Cannel Coal in the west of Fifeshire ; with Observa- 

 tions on the supposed Lacustrine Limestone of Burdie- 

 house. By Leonard Horner, Esq. F.R.SS. L. & E., and 

 F. G. S. 



In a fragment of this kind of coal there was accidentally found a 

 very fine specimen of a tooth, which the author considers to belong 

 to the Megalichthys Hibberti of Agassiz. It is similar to some of 

 those found in the limestone of Burdiehouse by Dr Hibbert, and is 

 almost identical with that figured at p. 183 in Dr Hibbert's Me- 

 moir, in the 13th volume of the Society's Transactions ; being about 

 two inches long, and seven-eighths of an inch at the base, longitu- 

 dinally striated, and covered with a shining enamel. 



The coal in which it was found was brought from Halbeath, 

 about two miles eastward of Dunfermline. It forms one of the re- 

 gular coal-measures, being associated with sandstones, shales, clays, 

 and beds of coal of ordinary qualities ; the shells abounding with 

 impressions of plants. The strata are subject to great disturbances, 

 there being five faults in the space of half a mile. There are no 

 trap-dikes, but there is an overlying mass of trap, which the author 

 believes to be connected with a deep-seated dike ; and it is proba- 

 bly to the intrusion of this igneous rock that the disturbances in 

 the stratification are to be ascribed. 



The occurrence of remains of the same sauroid fish that is found 



