296. British Association for the Advancement of Science. 
law of visible direction in monocular vision, it explains all those 
phenomena of vision by which philosophers had been so long per- 
plexed; and that vision in three dimensions received the most. 
complete explanation from Prof. W.’s researches. Sir J. Herschel 
characterized Prof-W.’s discovery-as one of the most curious and 
beautiful for its simplicity, in the entire range of ae 
optics. 
Rev. Charles Graves read a paper on, a General Catena 
Method. 
Sir T. M. Brisbane reported. the result of .an cxpheinnalld to de- 
termine the difference of longitude between London .and Edin- 
burgh. Having observed the surprising accuracy with which 
the difference of longitude of London and Paris had been ob- 
tained by Mr. Dent’s chronometers, he applied to him, and he 
very liberally placed at his disposal twelve of his valuable chro- 
nometers. With these, the differences of longitude of London, 
Edinburgh and’ Makerstouin, were taken ;.and by 4 mean of all 
the observations taken in going to the latter station and in return- 
ing, they were doen: to differ only by five one-hundredths of a 
secon 
A letter: from. the Astronomer Royal, G. B. shiny, was Ewell on 
ithe means of correcting the local magnetic action of the Compass 
‘in iron Steam-Ships. By an apparatus of his: invention, the 
local deviations were almost wholly cabrseted. © The description 
will probably be given hereafter. 
Prof. Lloyd read a paper entitled, “ iistinslasion i the obser- 
vations of the Magnetic Dip and Intensity in Treland, with ad- 
ditional elements.” It i is found that the annual decrease of the’ 
dip at Dublin is 2/38. The recent and more complete observa- 
tions of Sabine at London, make the annual decrease there 2/.40. _ 
Major Sabine spoke in reference to the Report on the Variations 
in the Magnetic Intensity, printed in the last volume. He ad- 
verted to the observations of Profs. Bache and Courtenay, made 
in New York and the adjoining States, and which Prof. B. is now 
engaged in connecting with Europe.. Until this comparison is 
complete, these observations determine the value of the magnetic © 
force at the stations at which they are made, relatively to each 
other, but not relatively to other parts of the globe. - It was for 
this reason that they were not available for Sabine’s Report, 
= ee the, general distribution of the magnetic — 
is . 
