Hyland— On the Mesolite {Galactite) of Kenbane Head. 417 



feature — the gelatinization with acids. The water all such mine- 

 rals possess is now separated into water of constitution and water 

 of crystallization. Under water of constitution is understood that 

 water which is in chemical, i.e. atomistic combination with the 

 atoms of the substance, and which is present, not as H 2 0, but as 

 H . . H ; whilst water of crystallization is considered as water* 

 which, owing to the action of molecular influences, is stored in a 

 condensed condition between the molecules of the substance. 1 It 

 is present in a definite chemical proportion, but is not an essential 

 portion of the compound, although, according to old Haiiy, " it is 

 necessary to its crystallization". 2 Still, though the difference in 

 theory is quite clear, it is often very difficult to decide whether the 

 water given off upon the application of heat is water of crystalliza- 

 tion, or whether it is produced by the combination of the hydrogen 

 and oxygen of the compound — a difficulty to which Fr. v. Kobell 

 has particularly called attention. 3 It seems, however, certain that 

 the water which is driven off only upon ignition (Gluhhitze) is 

 chemically combined ; on the other hand, it is not yet established 

 whether the water of crystallization is completely expelled at 100° 

 •or 120° C. Experiments upon the quantity of H 3 expelled at 

 various temperatures have been made by A. Damour ; 4 but the 

 question of the relation of the water was not attacked. Rammels- 

 berg, 5 in his Handbuch der Miner alchemie, makes allusion to the 

 subject, and considers as water of crystallization that water which 

 is lost at low temperatures and taken up again upon exposure to 

 free air. Yery interesting work has recently been executed in 



Mineralogy, 2nd edn., by J. Hyacinth de Magellan. London: 1788, vol. i., p. 244. 

 To p. 252 the Editor adds the following foot-note, which is not without interest : — 



"Mr. Pazumot thinks that the zeolites cannot be a volcanic production, but only a 

 secondary production formed by the decomposition of volcanic earths. Certainly pure 

 basaltes and volcanic lavas have the same component parts as those of the zeolites ; and 

 these last have not yet been found but among volcanic matters ; but as Mr. Faujas 

 observes, there are many instances of the true zeolites being quite buried within the 

 bodies of solid basaltes, some being only fragments of zeolites, and some having a com- 

 plete form ; which prove that they have been already formed before these volcanic masses 

 were produced by subterraneous fires (!)." 



1 Naumann— Zirkel, Mineralogie, 1885, 12te. Aufl., p. 225. 



2 Traite de Mineralogie. Paris: 1801, ii., p. 122. 



3 Sitzungsbericht der bayr. Akademie d. "Wiss. 11 Juni, 1870. 



4 Eecherches sur les proprietes hygroscopiques des mineraux de la famille des 

 zeolites ; Annales de chimie et physique. 3me. serie, tome 53, p. 438. 



5 Handbuch der Mineralchemie. Leipzig: 1875; 2te. Aufl., i., p. 123. 



