1870.] Chemistry. 109 



usually exhibiting a diameter of only 1 centimetre, but occasionally 

 some are found of two or three times that size. As a rule these 

 bubbles are very ephemeral ; now and then, however, it happens that 

 some may be caught along with a quantity of water in a small 

 beaker glass, and on the mercurial bubbles bursting, it will be seen 

 how very small a quantity of mercury these bubbles consist of. 

 Professor Hofmann mentions that he saw this experiment first 

 exhibited in the lecture-room of the Eoyal College of Chemistry, 

 London, when, twenty years ago, Professor Melsens, from Brussels, 

 was on a visit there. 



Caustic baryta is likely to become of considerable use for indus- 

 trial purposes. M. Nickles has described its mode of preparation. 

 It appears that four operations are required : — (1) Conversion of 

 native sulphate of baryta into sulphide of barium ; this is effected 

 in a continuous manner, in a peculiarly constructed furnace, the 

 sulphate being previously mixed with a reducing substance; (2) 

 the conversion of the sulphide of barium into hydrate of baryta, by 

 means of hydrated oxide of zinc ; (3) dehydration of the hydrate of 

 baryta by ignition along with sawdust ; (4) regeneration of the 

 substance which has served for the desulphuration of the sulphide 

 and obtaining of sulphur. 



M. E. Underhold states that the hardest steam-boiler incrus- 

 tations are formed when the quantity of carbonate of lime amounts 

 to from 20 to 25 per cent, of the entire mass. He has found, by 

 an experience extending over several years, that some kinds of clay 

 when suspended in the water contained in steam-boilers, prevent 

 the particles of carbonate and sulphate of lime dissolved in the 

 water, even if the latter is very hard, from clinging together and 

 becoming fixed to the sides of the boilers, forming there a hard 

 incrustation. A series of experiments, made on purpose and con- 

 tinued for a sufficient length of time to yield a reliable result, has 

 fully proved that the addition to the feed- water of the steam-boilers 

 of fatty clay, especially that known as fuller's-earth, entirely pre- 

 vents boiler incrustations, even where, of necessity, very hard 

 water has to be used as feed-water. A loose soft mud is deposited 

 as soon as the motion of the water due to the boiling ceases on 

 cooling. This mud readily runs off on opening the valve of the 

 boiler. 



Some valuable sulphur deposits have been discovered in the 

 island of Saba, Netherlands, West Indies. The rock composing 

 almost the entire formation of Saba is trachytic porphyry, which 

 contains glassy felspar and hornblende in crystals, disseminated 

 through a dark reddish-coloured vase. The sulphur deposit is 

 located on the northern part of the island of Saba, and extends for 

 a distance of more than a mile along the sea line. The stratum of 



