4.42 Life of Cavendish 



14. An Account of Experiments made by Mr John Macnab, at Albany Fort, 

 Hudson's Bay. (Phil. Trans. 1788, p. 166.) The points of easy congelation are 

 still further investigated, and illustrated by comparison with Mr Keir's experi- 

 ments on the sulphuric acid. It was found that the nitric acid was only liable 

 to the aqueous congelation, when it was strong enough to dissolve Jth of its 

 weight of marble; and that it had a point of easy congelation, when it was 

 capable of dissolving T Vin5> the frozen part exhibiting, in other cases, a tendency 

 to approach to this standard. Mr Keir had found that sulphuric acid, of the 

 specific gravity 1-78, froze at 46, and that it had another maximum when it 

 was very highly concentrated*. 



15. On the Conversion of a Mixture of Dephlogisticated and Phlogisticated 

 Air into Nitric Acid, by the Electric Shock. (Phil. Trans. 1788, p. 261.) Some 

 difficulties having occurred to the Continental chemists in the repetition of 

 this experiment, it was exhibited with perfect success, by Mr Gilpin, to a number 

 of witnesses. This was an instance of condescension, which could scarcely have 

 been expected from the complete conviction, which the author of the discovery 

 must have felt, of his own accuracy, and of the necessity of the establishment 

 of his discovery, when time should have been afforded for its examination. 



16. On the Height of the Luminous Arch, which was seen on Feb. 23, 1784. 

 (Phil. Trans. 1790, p. 101.) Mr Cavendish conjectures that the appearance of 

 such arches depends on a diffused light, resembling the aurora borealis, spread 

 into a flattened space, contained between two planes nearly vertical, and only 

 visible in the direction of its breadth : so that they are never seen at places far 

 remote from the direction of the surface; and hence it is difficult to procure 

 observations sufficiently accurate for determining their height, upon so short 

 a base: but in the present instance there is reason to believe that the height 

 must have been between 52 and 71 miles. 



17. On the Civil Year of the Hindoos, and its Divisions, with an Account of 

 three Almanacs belonging to Charles Wilkins, Esq. (Phil. Trans. 1792, p. 383.) 

 The subject of this paper is more intricate than generally interesting; but it 

 may serve as a specimen of the diligence which the author employed in the 

 investigation of every point more or less immediately connected with his 

 favourite objects. The month of the Hindoos is lunar in its duration, but solar 

 in its commencement; and its periods are extremely complicated, and often 

 different for different geographical situations: the day is divided and sub- 

 divided sexagesimally. The date of the year, in the epoch of the Kalee Yug, 

 expresses the ordinal number of years elapsed, as it is usual with our astronomers 

 to reckon their days : so that the year 100 would be the beginning of the second 

 century, and not the tooth year, or the end of the first century, as in the 

 European calendar: in the same manner as, in astronomical language, 1817 

 December 3id. i8h. means six o'clock in the morning of the ist of January 

 1818. 



* [Compare with these two papers the modern investigations of coexistent 

 chemical phases, and their applications to metallurgy and other sciences.] 



