Bath Literary and Philosopkicai Society. 223 



and that no dependence can be placed on any deductions from 

 mathematical investigations as to what has been termed cajOiZ/ary 

 at fraction, 



Monday, March 10. Dr. Wilkinson stated, that he had re- 

 ceived a letter from Mr. Bakewell, author of The Elements of 

 Geology of England, intimating that he had discovered in the 

 iieighboi'.rhood of Berkeley, Gloucestershire, basalt with coral 

 and shells imbedded in it ; a circumstance difficult to reconcile 

 with the theory of basalt being of igneous origin. The learned 

 Doctor also exhibited a specimen of the fruit of the locust-tree, 

 the hymencpa of the West Indies. It is a large pod containing 

 seeds surrounded by a saccharine pulp. Dr. W. remarked, that 

 it had been supposed by some, that this constituted the food of 

 St. John in the Wilderness, In Arabia, Numidia, Abyssinia, 

 and even among the Hottentots, the locust insect is a favourite 

 article of food, and used both in its recent and preserved state. 

 The locust alluded to in the Scriptures, is supposed to mean li- 

 terally the insect, and the wild honey a species of manna. 



A communication, from a member, relative to the appearance 

 of the aurora lorealis, as seen in Derby and its neighbourhood oa 

 Saturday the 8th of February last, was next read. It was ob- 

 served by Mr. Horner, that the reappearance of these lights 

 militates against the theory advanced by Dalton and Darwin, 

 of the coincidence of the vertex of these irradiations with the 

 line of no variation of the needle. The variation of the needle, 

 as observed at different periods at Greenwich, is as follows : 



In 1580, IP 15' eastward 

 I(;22, 6 ditto 

 1G34, 4 5 ditto 

 1657, no variation 



In IJ^S, 18" 6' westward 

 1751, 19 ditto 

 1772, 23 30 ditto 

 1786, 26 21 ditto 

 1790, 27 15 ditto 



Between 1G57 and 1790 the annual average was nearly 12" 

 18". After having been many years stationary, the needle is 

 now returning to t!ie north. 



The discussion of Dr. Wilkinson's Theory on the Rise of Fluids 

 in capillary Tubes next occupied the attention of the Society. 

 The Doctor remarked, that from experiments it appeared that 

 the rise of fluids is not exactly as the reverse of the diameters, 

 but nearly so ; the columnar pressure of fluids being as the area 

 of the base multiplied by the perpendicular height. Hence with 

 equal heights the pressure will be as the squares of their diame- 

 ters ; so that in a tube of one-tenth of an inch, and another of 

 one-twentieth, to render the quantmn of water in each tube the 

 «ame as asserted by Professor Atwood, the fluid ought to rise 

 four limes higher in the smaller tube than in the larger, which 



noway 



