424 



Prof. M. Simpson on the Formation of [May 23, 



It is then shown that the effects of inertia, which had been neglected 

 in finding the laws of the tidal movements, cannot be snch as to mate- 

 rially affect the accuracy of the results. 



In the first part of this paper I followed Sir W. Thomson in using 

 the equilibrium theory for the determination of the amount of reduc- 

 tion of ocean tides. But that theory is acknowledged on all hands to 

 be very faulty in its explanation of tides of short period ; hence a 

 dynamical investigation of the effects of a bodily yielding of the earth 

 on a tide of short period in a shallow equatorial canal appeared likely 

 to be interesting. This investigation is carried out in the second part 

 of the paper. The problem is simplified by supposing the circular 

 canal developed into a straight canal, whose bottom is constrained to 

 execute a simple harmonic wave motion. 



The result shows that the height of the ocean tide relatively to the 

 nucleus bears the same relation to the height of tide on a rigid nucleus 

 as in the equilibrium theory, and that the alteration of phase is the 

 same. This seems to increase the force of Sir W. Thomson's argu- 

 ment as to the rigidity of the earth. 



The chief practical result of this paper may be summed up by say- 

 ing, that it is strongly confirmatory of the view that the earth has a 

 very great effective rigidity ; but its chief value is, that it forms a 

 necessary first chapter to the investigation of the precession of viscous 

 and imperfectly elastic spheroids — an investigation which I hope to 

 complete very shortly. 



VI. " On the Formation of Chlor-iodide and Brom-iodide of 

 Ethylidene." By Dr. Maxwell Simpson, F.R.S., Professor 

 of Chemistry, Queen's College, Cork. Received May 7, 

 1878. 



(Preliminary Notice.) 

 CH 3 



Chlor-iodide of ethylidene | . This body I have succeeded in 



CHC1I 



preparing by two processes. 



First Process. — A quantity of iodide of ethylidene, which had been 

 prepared by Gustavson's method, and heated to 160° C. but not distilled, 

 was vigorously agitated for some time with a weak solution of chloride 

 of iodine without the application of heat. The excess of chloride was 

 then poured off, and the product well washed with dilute potash and 

 distilled. Almost the entire quantity passed over between 110 and 

 150° C. This yielded, on fractioning, a large quantity of fluid boiling 

 between 116 and 120° 0., most between 117 and 119.° This was the 

 body in question. The chloride of iodine used in this process was 



