WITH THOSE OF NEW YORK. 271 



sometimes formed in rocks of a different composition ; the mate- 

 rial of like nature, whether from attractive force, crystallization or 

 otherwise, commences to aggregate the mass. A small nucleus 

 is formed, and if there be no impediment it goes on increasing by 

 concentric coats, and by attracting the material of the same kind 

 to itself from all directions. If the resisting medium do not too 

 powerfully oppose the accretion of the particles, they unite in a 

 solid sphere : if the resisting medium overcomes the power of 

 attraction, concentric rings are formed, as in the diagram, Fig. 2. 

 Sometimes two centres are formed near each other, as in Fig. 1 ; 

 and in this case one side may increase faster than the other, the 

 matter between them being divided, or the two may finally unite 

 in one, producing the fantastic shapes often seen in Seplaria and 

 other accretionary forms. The nucleus is not always spherical, 

 and then neither will be the final production. Fig. 3 exhibits 

 concentric laminee with slightly undulating ones in the centre, and 

 shows a tendency to form another centre on the upper right hand 

 margin. The graphic effect of these appearances cannot be con- 

 ceived from the sketch given. In the face of the clifT, numerous 

 sections of concentric spheres were seen, and nearly all exhibited 

 in a greater or less degree the phenomena here described. 



This character, so well illustrated at this place, continues in 

 every locality, in greater or less degree, as far as examined west- 

 ward ; the ore frequently forming nodules or accretions. From 

 what I was able to learn from other observers in Michigan, 

 there is a considerable quantity of similar ore in the same situa- 

 tion in that State. 



In the vicinity of Cuyahoga Falls, the conglomerate may be 

 seen passing beneath the coal which is worked in several places 

 in that neighborhood ; the principal mines which I saw being 

 those on the farm of Henry Newberry, Esq. Below the falls the 

 Chemung group is distinctly characterized, containing however 

 few fossils compared with the same further east. I obtained 

 enough to convince me of the identity, and I have since received 

 from Mr. John Newberry several others, which at that time I did 

 not see. The most abundant fossil is a species of Strophomena. 

 Beside this, there is an Atri/pa, a Ci/pricardia, an Orbiada, a Lin- 

 gular a small crinoid, and one or two undescribed forms. 



