1835.] the Advancement of Science] " 219 



In Limerick the dip was 71°; in Dublin, it was less. It 

 increased towards the north-west, in the direction of the 

 west magnetic pole, 71J°. In Armagh it was about 7ri5J°. 

 The author remarked the utility of having magnetic ob- 

 servations made at different stations. An interchange of 

 needles was made between Captain James Ross and Captain 

 Sabine, by which their respective observations would be 

 made to correspond. 



31. Mr. Hamilton, 071 the Theory of Varying Orbits, He 

 explained the general nature of orbits, under the influence 

 of perturbations, expressed by Lagrange as a varying ellipse. 

 The author's method is a modification of this, by different 

 ellipses, founded on a former general method, in a some- 

 what simplified form. 



Mr. M'Cullagh mentioned some investigations of his 

 own, upon the same subject ; and stated, verbally, a rule 

 which he had deduced. 



Professor Powell stated certain difficulties of calculation 

 which had occurred in his optical researches, with a view 

 to elicit any assistance which the members of the Association 

 might be able to give in the solution of them. 



32. Mr. Kane, on the Interference of Sound. He referred 

 to Herschel's suggestion of the distinction of sound by inter- 

 ference, as analogous to the absorption of light. In trying 

 the experiment he found anomalies in certain cases. 



Mr. Addams remarked that the anomalies might easily be 

 explained, by considering the actual conditions of the case. 



Mr. Wheatstone made some remarks, and described ex- 

 periments which seemed to reconcile the anomalies alleged. 



Mechanical Science applied to the Arts. — The First Meeting 

 was held on Thursday, \^th August. Mr. Rennie, Presi- 

 dent; Dr. Lardner, Vice-President. 



1. Mr. Hodgkinson of Manchester detailed some experi- 

 ments in reference to the collision of beams and piles. This 

 communication formed the continuation of a former paper 

 read to the Association. The results were 1 : That when 

 cast iron beams were brought forcibly in contact with balls 

 of different kinds of metals of equal weights, the deflection 

 was the same in distance, whatever the nature of the metals 



