Geology and Mineralogy. 315 



less the result of molecular changes in its structure produced by 

 maintaining it at very high temperature ; and he finds manifes- 

 tation of the alteration in the change of thermo-electric power of 

 the carbon. — Phil. Mag., August, 1885, pp. 117-126. 



4. On changes produced by Magnetization in the Length of 

 Rods of Iron and Steel. — An abstract of an article on this subject 

 by Shelford Bid well, after mentioning the results reached by 

 earlier experimenters, goes on to remark that by using thinner 

 iron rods and greater magnetizing forces the curious fact was 

 established that if the magnetization be carried beyond a certain 

 critical point, the consequent elongation, instead of remaining 

 stationary at a maximum, becomes diminished, the diminution 

 increasing with the force. If the force is sufficiently increased, a 

 point is reached where the original length of the rod is totally 

 unaffected by magnetization ; and if the magnetization be carried 

 still further, the original length of the rod is reduced. It also 

 appeared that the position of the critical point in steel depended 

 in a remarkable manner upon the hardness or temper of the 

 metal. The author embodies his results for iron, steel and nickel 

 in a series of formal laws. — Proc. Roy. Soc, No. 237, p. 265. 



II. Geology and Mlnekalogy. 



1. Notes on some of the Geological Papers presented at the 

 Meeting of the American Association at Ann Arbor : * 



(1.) A. Winchell. On the Geology of Ann Arbor. The 

 following is a summary of the geological facts within easy reach 

 of Ann Arbor. Drift covers the nearest outcrop of rock 20 miles 

 away; depth of drift at the University 200 feet, at the Observa- 

 tory, 230 feet; on hills west and north probably 375 feet. Indi- 

 cations of terminal moraine. Kettle hole within a few rods. The 

 drift accumulations rest on the outcropping belt of Marshall 

 sandstone, trending northeast-southwest. Sheets of impervious 

 materials included, forming water basins, and this source of supply 

 is the basis of the water-works of Ann Arbor. Tabular limestone 

 masses imbedded in upper part of drift as formerly described by 

 the writer in this Journal, II, xl, 331-8; ascribed to action of ice- 

 floes in Scientific Monthly, Toledo, Oct., 1875, this Journal, III, 

 xi, 225-8 ; with additional facts in Proc. Amer. Assoc, xxiv, 1875, 

 pp. 27-43 ; differently explained by T. C. Chamberlin in Ann. 

 Rep. TJ. S. Geol. Surv., 1881-2, pp. 326-330. 



(2.) S. G. Williams. Traced the Lower Helderberg strata 

 into western New York. 



(3.) A. H. Worthed. On the Quaternary deposits of Illinois. 

 The author exhibited sundry sections obtained by borings in 

 central and southern-central Illinois. They showed generally that 

 the lower portion of the Quaternary formation is strictly stratified; 

 that no bowlder beds exist, but that bowlders are sparsely scat- 

 tered through the middle portions; that a dirt bed generally 



* For these notes this Journal is indebted to Professor Alexander Winchell. 



