332 



cessive addition of 10 per cent, of gold to the silver, the fusion of 

 which, when pure, marks the point of zero ; while that of gold is 

 reckoned at ten degrees. If minuter subdivisions were required for 

 particular objects of research, these might easily be made, following 

 always the decimal series. From the point of fusion of pure gold to 

 that of pure platina, the author assumes 100 degrees, adding to the 

 alloy which is to measure each in succession 1 per cent, of platina. 

 Whether these hypothetical degrees represent equable increments of 

 temperature is a question foreign to the purpose of this paper, and 

 must be the subject of future investigation. The author then enters 

 into a detailed account of the method he employed for insuring ac- 

 curacy in the formation of the requisite series of alloys, and of various 

 experiments undertaken to ascertain their fitness as measures of high 

 temperatures. The determinations of the heats of the different fur- 

 naces adapted to particular objects, are given in a tabular form. The 

 remaining portion of the paper contains the recital of the author's 

 attempts to determine by means of an apparatus connected with an 

 air thermometer, the relation which the fusing point of pure silver 

 bears to the ordinary thermometric scale. An extensive series of ex- 

 periments, of which the results are given in a table, were made with 

 this apparatus. From the data thus afforded, after making the ne- 

 cessary corrections, the author deduces the following results in degrees 

 of Fahrenheit : viz. A full red heat 1200; orange heat 1650; melt- 

 ing point of silver (which had been estimated by Wedgewood at 

 4717, and by Daniell at 2233,) 1830; of silver alloyed with one 

 tenth gold 1920. 



The paper is accompanied with drawings of the apparatus em- 

 ployed. 



On Captain Parry's and Lieutenant Foster's Experiments on the Velo- 

 city of Sound. By Dr. Gerard Moll, Professor of Natural Philo- 

 sophy in the University of Utrecht. Communicated by Captain 

 Henry Kater, V.P.R.S. Read January 17, 1828. [Phil. Trans. 

 1828, p. 97.] 



In this paper the author institutes a comparison between the re- 

 sults of the experiments on the velocity of sound made by Captain 

 Parry and Lieutenant Foster in the arctic regions, and those deduced 

 from the theoretical formula of Laplace. At the temperature of 

 170-72 of Fahrenheit, and with a barometric pressure of 29'936 

 inches, the mean result of all the observations gave a velocity of 

 103 6' 19 feet per second. With the same data, this velocity, by 

 calculation according to the formula of Laplace, would be 101 7' 72 ; 

 differing from the observed velocity by 17 '47 feet only. Similar 

 comparisons of particular observations, which are selected as being 

 made under favourable circumstances, with the deductions from 

 theory, are made by the author with but little variation in the results. 

 From the whole investigation, he draws the conclusion, that in very 

 high latitudes, where the cold is very intense, the data on which the 



