360 [Proc. B.N.F.C, 



condition under which each was produced, the lecturer went 

 on to say that the nature of this columnar basalt had been 

 discussed by the learned for ages, and in explanation of the 

 phenomena various theories had been suggested, such as 

 crystallisation, cleavage, shrinkage, and an accumulation of 

 globular concretions. The late Dr. James Thompson had 

 propounded a theory assuming that the cooling and shrinking 

 mass of basalt cracked into columns as starch cracked in drying, 

 and that the cross fractures and joints were caused by the strain 

 set up in the axis of the columns owing to the expansion of the 

 outer surface of the column. It was more probable that the 

 strain in the centre was caused by the further contraction of 

 the centre portion of the column after the outside portion 

 became rigid. It was clear, however, that the fracture com- 

 menced in the centre of the column and extended to the outside, 

 the difference in the sections of the columns varying from three 

 to nine sides. It was not incompatible with the theory 

 of crystallisation, but the marked difference of the angles 

 of the existing columns was directly against the theory of 

 crystallisation. Speculations as to the deposit of the columns 

 might be set at rest, for they were shown their full strength 

 elsewhere on the cliffs, from which they differed only in their 

 more regular form. The various points of interest in the 

 vicinity of the Causeway were then profusely illustrated by a 

 series of views. As to the methods for reaching the Causeway 

 from the headlands above it, they had, he said, several references 

 in the published descriptions from the seventeenth century to 

 the present time. In the "Philosophical Transactions" for 

 April, 1693, a letter was published from Sir Richard Burkeley 

 to Dr. Lister, in which he gave a description of the Causeway, 

 and said — " When you come to the precipice there is no going 

 down there it is so perpendicularly steep, but with much labour 

 and some hazard it may be climbed up. By other ways and 

 winding up one comes down to the strand which forms the foot 

 of this precipice, then runs out northward into the main ocean 

 a raised causeway." In 1708, Dr. Molyneaux visited the 



