Lowell. — Geological Facts. 345 



injected the other ; it is however beyond our power to assign a rea- 

 son why the igneous action below, should produce trap abundantly 

 in one place, and granite in another, and at a very short distance. — 

 On the Red Mountain in New Hampshire near Lake Winnepiseogee 

 we have seen a powerful dyke of trap traversing granite, which of 

 course proves that whether contemporaneous or not, the materials of 

 tlie two rocks must have been concocted in, and ejected from, the 

 same igneous focus. The instances at Lowell go far to demonstrate 

 that the causes which liave generated granite and trap are the same, 

 operating under unknown circumstances of difference, and indeed we 

 shall probably not go too far if we regard all igneous rocks as mere 

 modes in the operation and result of one and the same cause, due 

 allowance being made for variety of circumstances and of materials 

 upon which the lire has operated. 



It is worthy of observation, that at the rail road section near Low- 

 ell, there are numerous veins of quartz, some of them of great thick- 

 ne'ss which are found both among the trap and the mica slate, but 

 principally among the strata of the latter, pursuing the course of the 

 structure of the rock excepting where tJie veins or portions of them 

 have been detached by the trap, and are found intermingled with, or 

 cut off and surrounded by it. The quartz veins were doubtless, 

 originally component parts of the mica slate rock, to whose consti- 

 tution they indeed essentially belong. 



On various parts of the ledges through which the rail road section 

 passes, but especially, at the entrance near the village of Lowell, 

 there are considerable diluvial deposits — gravel, sand and bowlders 

 mingled in confusion ; among the bowlders are many transported 

 rocks unlike the ledges below, but lying in juxta-position with their 

 ruins, which have been detached in the progress of time by meteoric 

 causes and perhaps by convulsions. 



Indeed, in every part of Lowell, the observer is struck with the 

 great abundance of bowlders and detached and travelled masses both 

 lying on the surface and buried in the gravel, clay and sand. In 

 digging into hills and into the earth, in other situations, they find 

 such great numbers of bowlders that they appear as if they had 

 been congregated by design and tlie laborers arrange them — for con- 

 venience, in immense groups. 



It gives us pleasure to state that a very correct and graphic delinea- 

 tion of the rail road cut, was kindly furnished to us by JMr. Duesbury 

 of Lowell, in which the great feature?, which we have attempted to 



Vol. XX VII. -No. 2. U 



