170 On the Relation of Acids and Alkali i 



Example. — Given the altitudes of the sun 1S° U' and 

 17° 13', interval one hour, and the sun's declination 20° S. to 

 find the latitude, it beuig by account about 50** N. 

 lfi° 41' 



17 \•^ 



Rum .3(3 54, 

 Diff. £ 28, 



9-115698 sin 

 9-97298() cos 



half sum 18° 27' half interval 7° SCX 

 halfdift: 1 14 



r .30' 



20 sin 9-534053 



9-088684 sin I 7 3 sect -003296 



II 110 10 cos 9-537348 



•00329() 

 9-500342 sin 

 9-999899 cos 



cosect -911030 



18° 27' cos 9-977003 

 1 14 sin 8-332924 



•008103 sect III 9 35 sin 9-221037 



IV 71 8 cos 9-509fi40 



V 39 2 



cos 9-993897 

 cos 9-890298 



Lat. 49 59 sin 9-884195 



I liave introduced the rule in the above form among the 

 young navigators in this Institution ; and if what I have said 

 may lie the means of drawing the attention of practical men 

 to the subject, my object in writing these observations will be 

 attained. 



XXVIII. On the Relation of Acid% and Allcalis to vegetaUe 

 Colour^ and their Mutatinna. thereby. By John Muriiay, 

 F.L.S. M.G.S. M. IV.S. S^x. 4r. 



To the Edi tarn of the Philosophical Mfigazinc and Journal. 

 ^ July 9,1822. 



Gentlemen, — 1 o u had the goodness to insert in a former 

 Number of the Philosophical Magazine (volume Iviii. p. 273) 

 a few remarks of mine on the change of vegetable colours by 

 metallic salts ; and it is more than a twelvemonth since I have 

 in my prirlectious pointed out that the mere change of colour 

 produced by acids and alkalis afforded no certain index of 

 their nature. I showed the action of salts of iron, &c. on sy- 

 T\\\) of violets, &c. in my experiments at the Surry Institution, 

 both in my jiublic discussions and to several individuals in the 

 laboratory of that Institution. 



At page 274 of the Philosophical Magazine, vol. Iviii. my 

 language, one would tliink, is emphatic enough. " It seems 



evident 



