72 hitelligence and Miscellaneous Articles, 



stars less than half the sun's mass. But this point, which is de- 

 serving of attention, cannot be established until the observations 

 shall be sufficient to determine the elements accurately. When long- 

 continued observations of the places which the double star occupies 

 amongst the small stars which surround it, shall have led to the 

 knowledge of its centre of gravity, we shall be enabled to determine 

 the two masses separately. But we cannot anticipate the time of 

 these further researches. 



I have here troubled you with many particulars ; but I trust it is 

 not necessary to offer any excuse for this, since a correct opinion as 

 to whether the investigation of the parallax of 61 Cygni has already 

 led to an approximate result, or must still be carried further before 

 this can be affirmed of them, can only be formed from the knowledge 

 of those particulars. Had I merely communicated to you the re- 

 sult, I could not have expected that you would attribute to it that 

 certainty which, according to my oAvn judgment, it possesses. I 

 have the honour to be, esteemed Sir, yours, F. W. Bessel. 



XIV. Intelligence and Miscellajieous Articles. 



SILICATES OF SODA. 



MFRITZSCHE has described two crystallized compounds of 

 • silicate of soda and water in a memoir read before the Im- 

 perial Academy of St. Petersburgh. 



When silica is dissolved to saturation in a solution of caustic 

 soda, a liquid is obtained, which is capable of being almost entirely 

 converted into crystals. If the solution be concentrated, a crystal- 

 line mass is formed in a few days ; whereas if it be moderately di- 

 luted, it deposits crystalline radiated hemispherical masses, or scales 

 or laminae composed of crystals which are more or less distinct. 

 When this compound is prepared on a large scale, crj^stals are ob- 

 tained of the size of a pea, wliich are perfectly formed, and have 

 polished surfaces ; these are the crystals which were submitted to 

 analysis, and were used for the determination of the crystalline 

 form ; this salt was analysed in the usual way ; that is, it was de- 

 composed by hydrochloric acid, and the quantities of chloride of 

 sodium and silica determined ; 66" 8 parts of the crystals, pulverized 

 and pressed between folds of paper to remove their moisture as 

 much as possible, gave 14-4 of siUcaand 27-5 of chloride of sodium, 

 which is equivalent to 14" 6 of soda ; the quantity of water is then 

 37"8 or 56'o9 jjer cent. On exposing some entire crystals, but 

 ■which probably retained a little moisture, to a strong heat, the loss 

 amounted to 5 7 '23 per cent. The salt may therefore be considered 

 as composed of 



By nnalvsis. Theory. 



Silica 21-55 21-5'2 



Soda 21-86 21-86 



Water 56-59 56-62 



100- 100- 



The author represents it by Na^ Si^ -|- 27 H. 



