AMERICAN INSTITUTE. 571 



several acres of ground. They have two stores — one of which is 

 300 feet in length, and holds from 300,000 to 400,000 pounds 

 w^eight of ultramarine. This color undergoes eighty different 

 processes before it is ready for use. It is now applied to coloring 

 cloth, woolens, tapestry, paper, sealing waxes, besides its use by 

 artists. 



Ultramarine originally made from the Lapis Lazuli, is a very 

 beautiful and very permanent blue. The Lapis is found in masses 

 or nodules; they are composed chiefly of silica and alumina with 

 about 20 per cent of soda, and some peculiar combination of sul- 

 phur, to which it probably owes its color — it is often sprinkled 

 with yellow pyrites. We have it chiefly from Persia, China and 

 Russia, 



It is now prepared in France and Nuremberg, of equal beauty 

 to the Lazulite, and at a very moderate price. Mr. Gmelin of 

 Tubingen, considers the sulphuret of Sodium to be the coloring 

 principle, both of the Lapis Lazuli and of this artificial color. 

 The latter is made by adding freshly precipitated silica and 

 alumina mixed with sulphur to a solution of caustic soda; the 

 mixture is then evaporated to dryness; the residue is then placed 

 in covered crucibles and exposed to a white heat, by which, when 

 the air is partially admitted to it, a dark blue mass is obtained. 

 This is then reduced to an impalpable powder, silica 36, alumina 

 36, soda 4, and sulphur 3. 



Mr. Tillman read the following letter from Mr. B. H. Wright, 

 in relation to the cause of steam boilers exploding. 



Rome, N. Y., Dec. 11, 1856. 



Dear Sir: In conversation with you a short time ago I 

 stated to you, verbally, my own views as to the cause 

 of boiler explosions, and as we considered the subject one of the 

 greatest practical importance, I gave you a partial promise that I 

 would put my thoughts on paper, to the end that my theory may 

 be publicly commented on and controverted if erroneous. I have 

 never seen this theory advanced any where, and the like you 

 stated on your part; your acknowledged scientific attainment and 

 research lead me, therefore, to the belief that I may confier a bene- 

 fit in thus giving publicity to my views through you. 



I liave for some time believed that the assumed cause of the 

 explosion of steam boilers, or more correctly, evaporators, has 

 been, and still continues, a source of mischief. Public opinion 

 seems to have settled down quietly into the belief that the water 

 becoming low in the boiler, a portion of the latter above the sur- 

 fcice of the water becomes heated to redness, so that by renewed 

 supply of water this rises and covers this superheated surface, is 



