D.Kirhwood on the Sun-spot of June, 1843, 275 



Ms the burner which has been described in an article on flame- 

 heat in this Journal, II, vol. 1, p. 341. The upper open- 

 ing of it is a slit from 1| to 2 mm. in width, and from 3^ 

 Til 44- cm. long, and when used is brought within about two 



...'I'the lowest point of the crucible, the end of the flame 

 playing around the lower end of the crucible ; the gas en- 

 he lower part of tbe burner by two small holes of one- 

 - X iron til of an inch, furnishing at one inch pressure about b^ 

 cubic feet of gas per hour; the precaution must be observed 

 already referred to, in heating the crucible at first gently above 

 the mixture. It is surprising to see the effect produced by this 

 simple burner as here used ; 8 grams of precipitated carbonate of 

 lime can be decomposed to within two or three per cent in one 

 hour, and when mixed with silica or a silicate, in a very much 

 shorter space of time ; although in my analysis I employ owq 

 hour as it requires no attention after the operation is once start- 

 ed. This form of furnace and crucible is found to be conven- 

 ient for other operations. 



Although the details here given are long, the time occu- 

 pied in the analysis is short, and the necessary precautions are 

 of a simple character, so much so, that results obtained by stu- 

 dents in beginning chemical analysis have been found by me 

 far more reliable and less variable on the alkalies of the sili- 

 cates than on any of the other constituents. Good alkah deter- 

 minations can be made in three hours or less from the com- 

 mencement of the operation, hastening the evaporation by 

 more direct application of the heat, which of course requires 

 more close watching 



. It is a common practice of mine, when a silicate presents 

 Itself of which there are no physical means of ascertaining its 

 nature, to make at once an alkali determination, which not 

 infrequently indicates immediately what it is if it be a known 

 suicate containing an alkali ; and if an unknown compound, 

 the analysis made is one step in 



Art. XLl.~On the Great Sun-spot of June, 1843 ; by Professor 

 Daniel Kirkwood, Bloomington, Indiana. 



One of the largest and most remarkable spots ever seen on 

 Jhe sun's disc appeared in June, 1843, and continued visible to 

 tte naked eye for 7 or 8 days. The diameter of this spot was, 

 according to Schwabe, 74,000 miles; so that its area was many 

 times greater than that of the earth's surface. Now, it has been 

 •observed during a number of sun-spot cycles that the larger 

 ^Pots are generally found at or near the epoch of the greatest 



