18 JOURNAL OF THE [January, 



currents from distant centres of eruptive activity, and finally 

 settling down on some aqueous area, as a gentle and intermitting 

 rain of mineral particles, during a lengthy period of time. The 

 deposit from which the specimen came is five feet in thickness, 

 and is known to underlie a relatively wide area. Intimately asso- 

 ciated with this mineral basis are several kinds of fossil organic 

 microscopic remains, as smooth, non-tubercular, arcuate sponge 

 spicules, crystalline spheres, intermediate in their characters be- 

 tween the polycistinse and the fossil gemmules of sponges. The 

 spheres have in some instances surface ornamentation of minute 

 bosses, and in others short pyramidal processes or points, giving 

 them a stellate appearance. These spherules had never hitherto 

 been observed by me in any of the many preparations of fossil 

 ■earths examined. I also saw a few discs, which may be diatoms, 

 but they were unfamiliar shapes to me. 



" Touching what has preceded, it is a matter of geological record 

 that in the territory contiguous to the canons of the Colorado 

 River, and between the Rocky Mountains and Sierra Nevada, 

 there have been observed vast deposits or strata of fresh-water in- 

 fusorial origin, alternating between beds of volcanic tuffs, lava, 

 and other phenomena of volcanic activity characterizing the 

 struggle between the igneous and aqueous elements for supremacy, 

 in that rock-ribbed region of the earth, now in a state of compa- 

 rative quiescence. The deposit varies in its composition. Some 

 of the material is as white as chalk and has no admixture of 

 alumina to bind the grains together, and it can be dissipated as 

 dust by dry brushing. When a mount of this is made it shows 

 purely the glassy, angular plates, and nothing else. The eco- 

 nomic value of the deposit, either as tripoli or kaolin, has 

 not been overlooked by the commercial instinct, and a sample of 

 the porcelain made from it, and just received from England, 

 shows that it is not adapted to making white porcelain or china- 

 ware, as a cube of it burned into a sort of salmon-colored, trans- 

 lucent glass. A previous trial of it at Pittsburg reported it as 

 unfit for porcelain ware, on account of an oxide of iron that 

 contaminated it." 



On motion the thanks of the Society were tendered Mr. Cun- 

 ningham for this donation and communication. 



Mr. Stephen Helm read the paper announced on the programme, 



