British Association for the Advancement of Science. 113 



ductors of electricity, and freely connected by efficient conduc- 

 tors with the sea, the electrical agency would have an unlimited 

 and easy source of diffusion in all directions, and hence the ship 

 would be safe from the moment the flash struck the mast head. 

 From his inquiries it appeared that in 100 cases of ships in the 

 British Navy struck by lightning, the number struck on the 

 main-mast were to those struck on the fore-mast as 2 : 1 ; to those 

 struck on the mizen-mast, as 10 : 1 ; to those struck on the bow- 

 sprit, as 50 : 1. About one ship in six is set on fire in some part 

 of the hull, sails or rigging. In one half the cases some of the 

 crew were either killed or wounded. In the 100 cases alluded 

 to, 62 seamen were killed, and about 114 wounded. These are 

 exclusive of one case of a frigate, in which nearly all the crew 

 perished, and of 12 cases in which the numbers killed or wound- 

 ed were set down in the accounts given as several or many. In 

 these 100 cases, there were damaged or destroyed 93 lower 

 masts, principally of line-of-battle ships and frigates, 83 top- 

 masts, and 60 topgallant-masts. 



A notice was read, from Dr. Robinson, on the determination 

 of the arc of longitude between the observatories of Armagh and 

 Dublin. In September, 1838, Mr. Dent, by means of twelve 

 chronometers, determined the longitude of Dublin to be +25m. 

 21. 08s., longitude of Armagh -{-26m. 35.44s. Subsequently, by 

 means of rocket-signals. Dr. R. found the difference between 

 Armagh and Dublin to be Im. 14.258s. or .Is. less than the chro- 

 nometrical determination. 



The Longitude of New York City Hall was determined by 

 Mr. E. J. Dent, by means of chronometers sent out by the 

 British Glueen, in July, 1839, to be +4h. 56m. 3.55s. which va- 

 ries less than 3s. from the previously received determination. 

 (See this Journal, vol. xxxvii, p. 400.) 



Prof Whewell made some remarks on Dr. Wollaston's argu- 

 ment on the question of the infinite divisibility of matter, drawn 

 from the finite extent of the atmosphere. Dr. W. imagined that 

 if the extent of the earth's atmosphere be finite, air must consist 

 of indivisible atoms, since he assumed that the only way in 

 which we can conceive an upper surface of the atmosphere, is by 

 supposing an upper stratum of atoms, the weight of which, 

 acting downwards, is balanced by the repulsive force of the in- 

 ferior strata acting upwards. Prof W. contended that such a 



Vol. xxsviH, No. 1.— Oct.-Dec. 1839. 15 



