BULL. GEOL. SOC. AM. 



VOL. 25. 1913, PL. 24 



BOULDER OF PILLOW BASALT 



This boulder lies at the foot of thp cliff below the quairy and observation tower, east of 

 Greenfield, Massachusetts. The interstitial matter is a mixture of sand and glass (tachylite), 

 much of which shows flow structure. To the right of the watch and chain and extending 

 upward twice the length of the chain a series of four rounded masses are connected by narrow 

 necks and send out small lobes. "The effect of the jiile of great round blocks, with compara- 

 tively small amount of interstitial matter, can only partly be given by the photograph" (Emer- 

 son). Reprinted by permission of Prof. B. K. Emerson from Bulletin of the Geological So- 

 ciety of America, volume 8, 1897, plate 5. 



