PURGATORY. 29 



quartz rock passing into mica slate with a cement of talcose slate : the nodules varying 

 from the size of a pigeon's egg to four and even six feet in their longest diameter ; and so 

 arranged that their longest diameters are uniformly parallel to one another, lying in a north 

 and south direction." The conglomerate is divided by fissures running east and west per- 

 pendicular to the horizon, and parallel to one another, from 10 to 20 feet apart. These fis- 

 sures divide the thick masses of conglomerate so perfectly that they seem as if cut through 

 by the sword of some Titan. The nodules through which the fissure passes, are divided 

 very neatly, and the parts present even surfaces, so as to give the rock quite a peculiar 

 aspect." 



These facts were repeated in the subsequent Reports in 1835 and 1841 upon Massachu- 

 setts. But it was not till we found an analogous conglomerate at intervals along nearly 

 the whole western side of the Green Mountains, that the special bearing of the facts 

 above mentioned upon metamorphism occurred to us. Two of us then (1859) visited 

 Newport to get a clearer view of the facts, in the hope that they would help us unravel 

 better the intricacies of the Vermont conglomerates. One of us that same year gave a 

 paper on the subject before the American Scientific Association, as it was developed at 

 Newport and at East Wallingford, where an interesting locality had been discovered by 

 one of our number (A. D. Hager). In 1860 another of our number (c. H. H.) brought 

 the subject again before the Scientific Association. But it was not till since that time 

 that the last link in the argument was supplied by a visit to a locality in Plymouth, Vt., 

 which was also discovered by A. D. Hager. We will try now to state the facts and 

 conclusions as they have been gradually worked out by us. If any should wish to verify 

 our statements, and see the force of our reasoning, we advise them to visit the different 

 localities in the order in which we describe them. For the processes begun at Newport 

 seem to be carried to their completion in Vermont. 



Perhaps the best place to visit the Rhode Island locality is at the well known Purgatory, 

 two and a half miles east of Newport, and within the limits of Middletown. According to 

 the paper of c. H. H., read before the Scientific Association in August, 1860, the belt of con- 

 glomerate commences a little south of Purgatory, is a mile wide, with interstratified belts 

 of slates, and extends northeasterly probably as far as Sandy Point in Portsmouth, some 

 five and a half miles. It shows several folds, is underlaid by a gritty schist, or sandstone, 

 and itself underlies the coal measures. " It is a coarse conglomerate, composed of elon- 

 gated and flattened pebbles, from the smallest size to bowlders nearly twelve feet long, 

 cemented by a meager amount of talcose schist or sandstone," with numerous small 

 disseminated crystals of magnetite. The pebbles are mostly a fine grained or compact 

 quartz rock, which when partially decomposed appears like sandstone ; not unfrequently 

 the pebbles seem to pass into an imperfect mica schist, and show lamination. A few of 

 them are gneiss, and probably granite, and occasionally hornblende rock. In their short- 

 est diameter they rarely exceed a foot, while in length, one, two and three feet are very 

 common, and a few may be seen from four to six, and one at least as long as twelve feet. 

 The following facts as to the pebbles are of the most scientific interest : 



1. They are elongated often very much in the direction of the strike. 2. They are 

 flattened, but not so strikingly as they are elongated. 3. They are indented often deeply 

 by one being pressed into another. 4. They are sometimes a good deal bent, sometimes 



