ABSTRACTS AXD DISCUSSIONS OF PAPERS 51 



is subjected. On the contrary, water can exist in solution in liquid magmas, 

 and as such unquestionably plays a very important role in geologic processes 

 whicli go on at temperatures up to 1,000° or higher. The presence of water 

 in such solutions has three main effects, namely, it increases the fluidity of 

 tbe melt, lowers the temperature at which crystallization begins, and facilitates 

 the process of crystallization ; these effects are marked even when the quantity 

 of water is relatively small. These facts, which have an important bearing 

 on certain phenomena of volcanism and igneous intrusion, were discussed and 

 illustrated. 



Presented in abstract extemporaneously. 



Discussion 



Prof. J. Volney Lewis: It is a well known fact tbat fragmeutal volcanics 

 of acid character are far more abundant than basic ones. Some of us are 

 accustomed to attribute this to the greater abundance of water in siliceous 

 magmas, as a rule, or to their greater viscosity and hence greater resistance 

 to the escape of this water during eruption. May it not be possible that the 

 difference is in reality due, in part at least, to the greater capacity of basic 

 magmas for retaining water in solution until it is gradually released by 

 crystallization or imprisoned permanently in glass? I should lie glad to know 

 whether or not the investigation of which Doctor Morey has spoken might 

 throw light on this question. 



Doctor Morey replied briefly to Professor Lewis's remarks. 



"PELE'S TEARS 1 '. AND THEIR BEARING ON THE ORIGIN OF ALSTRALITES 



BY E. S. MOOUE 



CONTENTS 



I'age 



Introduction 51 



Characteristics and origin 52 



Comparison with similar bodies 53 



Chemical constituents 54 



Conclusion 5"> 



Introduction 



Among tbe problems confronting tbe Australian geologists few offer more 

 interesting material for speculation than the question of the origin of tbe aus- 

 tralites. These peculiar bodies liave been known by various names, such as 

 obsidian buttons, obsidian bombs, and obsidianites. They somewhat resemble 

 in composition and form tbe moldavites and billitonites. so Suess 1 has applied 

 the name australites to such bodies from Australia, while he uses the term 

 tektites to cover all bodies of this type. 



It is not the object of this paper to go into a detailed discussion of the aus- 

 tralites, as they have already been described very fully by several of the 



1 Franz Suess : Die Herkunft der Moldavite and verwandter. Glliser Jahrb. d. k. k. 

 Geol. Reichsanstalt. Heft 2, vol. 50, 1900. 



