ABSTRACT OF PROCEEDINGS. xlv. 



ores be found with only 0*1 per cent, of iodine, it might be profitable 

 to extract the same by sublimation. The value of the iodine in a 

 ton giving 0*1 per cent., would be 30/-, and he estimates the cost 

 of extraction at 3/-. The total value, however, of the world's 

 production of iodine in 1896 was only £350,000. 



3. "Orbit Elements Comet I. 1899 (Swift)," by C. J. Merfield, 



F.R.A.S. 



This paper contains the results of an investigation of the orbit 

 of the comet. In the prefatory remarks the author directs atten- 

 tion to several interesting physical aspects of this apparition. 

 During 1899 May, the comet was seen with a double nucleus, the 

 observed distance between the components increasing to some 

 extent during an interval of a few days ; part of this recession 

 from one another may have been due to an actual separation of 

 the nuclei, but the author has not examined the question critically. 

 Photographs of great value were taken at the Lick Observatory, 

 California; these show some interesting changes in the appearance 

 of coma and tail of the comet, that will be of interest to those 

 who work in this department of astronomy. The orbit elements 

 have been deduced from the observations taken at most of the 

 leading observatories. Sixteen equations of condition have been 

 employed in finding the corrections to the assumed parabolic 

 elements. The result of the investigation seems to indicate that 

 the geometrical figure described by this comet is an hyperbola. 

 Firstly, it has been taken for granted that no correction is necessary 

 to the eccentricity unity of the assumed elements, thus another 

 set of parabolic elements is obtained, and it is shewn that these 

 are more satisfactory, the sum of the squares of the residuals 

 reducing from 10 4 x 155 to 10 4 x 04 - l. Secondly, in this case the 

 author has made no assumption as to the form of the orbit, and finds 

 that a positive correction is required to the assumed eccentricity, 

 viz., unity, indicating therefore hyperbolic motion; the sum of 

 the squares of the residuals being most satisfactory, and reduced 

 to 10 4 x 0*01. In his concluding remarks the author states, that 

 the perturbations have been excluded from the calculation, as 



