21 



tude at the same places, a calculation with the corresponding data 

 gives the height 65*4 miles. 



These last three results are remarkably in accordance with each 

 other, but considerably different from those for other places at nearly 

 the same time ; so that probably the method which was used, of ob- 

 taining a base line by projecting the places of observation upon an 

 intermediate magnetic meridian, is only approximately correct, from 

 the course of the arch over the earth's surface, rather than geome- 

 trical reasons. 



Another arch was noted by most of the observers from 10 h 34 m 

 to 10 h 45 m . The observations at Dent at 10 h 40 m , and Heron Court 

 at 10 h 37 m , give the height of the upper edge 59*4 miles. 



An observation made by the author on the extent of the arch, on 

 September 17, upon the horizon at 8 h 40^ m , and its altitude, for ap- 

 plication to the formula he has given in the Edinburgh Journal of 

 Science, before it was joined with the Philosophical Magazine, for de- 

 termining the height from observations at one place by the help of 

 an hypothesis, gave the height 53*9 miles, which is a near approxi- 

 mation to the height found by the trigonometrical method for 

 8 h 25 m . 



The author concludes that the meteor occurs immediately beyond 

 the ordinary limits assigned to the earth's atmosphere, and from that 

 to very much greater altitudes, as shown by many other calcula- 

 tions ; and states his conviction that the meteor will be some time 

 observed with much more accurate means than hitherto, from its 

 connexion with the earth's magnetism. 



February 23, 1846. 



Analytical Investigation of the Disease prevalent in the Potato 

 during the year 1845. By Geo. Kemp., M.D., Pet. Coll. 



This communication may be resolved into two parts ; the analysis 

 of the diseased portion of the potato, as compared with Boussin- 

 gault's analysis of the healthy tuber, and certain deductions derived 

 from the empirical formulae proposed as representing their respective 

 compositions. 



The author recognises three stages of the disease : the first ap- 

 pearing as dark brown patches under the skin ; the second as striae 

 of the same colour proceeding towards the centre ; and the third as 

 a soft, pultaceous, blackish, and offensive mass, in which all traces 

 of organization are lost. 



From the impossibility of isolating the portions affected by the 

 disease, in the first two stages, from the surrounding sound parts, 

 the examination was principally directed to the third stage. 



A potato having been selected in which the above characters 

 were well-developed, a sufficiently large portion for comparison still 

 remaining perfectly sound, gave the following results as indicative 



