396 



SCIENCE. 



[N. S. Vol. XI. No. 271. 



understands it, entirely on the petrographic 

 ctiaracter of the rock, as it contains no fossils 

 and on its relation to the Carboniferous de- 

 posits in the hills north of the mine. Mr. 

 Dumble has studied this sandstone, if it really 

 be such, with considerable care, and finds it to 

 occupy a position much lower in the geological 

 scale than had been previously thought — that 

 it is, in fact, below the Texan Group of Com- 

 stock — that is, at the very base of the sedimen- 

 tary series. He does not believe that it is a 

 part of an immense mass or boss of igneous 

 material. 



Mr. A. C. McLaughlin, for several years past 

 connected with the Geological Survey of Mary- 

 land, gave an account of the work as conducted 

 by that organization in the western part of the 

 State. 



Professor T. U. Taylor, of the Department of 

 Engineering, read and commented upon a com- 

 munication received from Professor W. H. 

 Echols, of the University of Virginia, on the 

 ' Measure of Earthwork,' in which the prismatic 

 formulse were employed. 



Dr. S. E. Mezes followed with a paper on 

 'Monogamous Marriage,' in which he gave an 

 account of this institution and of the rules and 

 customs by which it has been maintained. 

 That this institution is adapted to the highest 

 civilization was shown in the fact that by it, 

 and it alone, could be made a home, and 

 that the home-training of children produced 

 the highest and best results socially. The paper 

 was both thoughtful and candid and received 

 the hearty approval of all who heard it. 



F. W. 8. 



Univbesity of Texas. 



DISCUSSION AND COEBESPONDENCE. 



MARGINAL TABS FOE LOGAEITHM TABLES. 



To THE Bditoe of Science : Will you permit 

 me, through the columns of Science, to bring 

 to the attention of users of my ' Computation 

 Rules and Logarithms,' a set of 'Marginal 

 Tabs ' for use in that book. The tabs are ar- 

 ranged for the five-place tables of logarithms 

 of numbers and of the trigonometrical functions. 

 They not only materially lessen the time re- 

 quired to find any logarithm or antilog in the 

 use of the tables to five places, but they render 



the table even more speedy than the ordinary 

 four-place table for obtaining the logarithms or 

 antilogs to four places, while also much lessen- 

 ing fatigue and liability to mistake, no interpo- 

 lation being required. The printed tabs, with 

 directions for their application and use, form a 

 leaflet which will be mailed by the author on 

 receipt of twenty-five cents. Copies of the 

 errata of the first (very thick paper) impression 

 of the Tables, but which have been corrected 

 in later impressions, will be mailed to holders 

 of that edition on receipt of a stamped and ad- 

 dressed envelope. 



S. W. HOLMAN. 



18 Elm Steeet, Beookline, Mass., 

 February 24, 1900. 



NOTES ON PHYSICS. 

 In the London Electrician is a report of some 

 recent experiments of Professor S. Lussana on 

 the variation of resistance under high pressures, 

 up to 1000 atmospheres. He found the resist- 

 ance to decrease with increase of pressure, and 

 obtained the following coeflicients per atmos- 

 phere. 



Lead 194 x 10"' 



Iron 38 Argentana 9.7x10"' 



Silver 32 Nickelina 7.4 



Copper 31 Constantea 7.9 



Platinum 24 Manganin 5.6 



Nickel 19 Brass 4.3 



The curves of decrease of resistance were 

 slightly concave toward the axis of pressure, 

 showing a tendency toward a minimum. 



The resistance did not return to its normal 

 immediately on removal of the pressure. In 

 the case of platinum which had been under a 

 pressure of 500 atmospheres for one hour, the 

 resistance, on removal of the pressure, increased 

 rapidly for ten minutes, and then quite slowly, 

 taking about one hour to return to approxi- 

 mately its normal. Held under the same pres- 

 sure for 24 hours, the curve showing its return 

 with time to normal resistance is very interest- 

 ing, rising in about 50 minutes to normal, going 

 above, returning again to normal in about 7J 

 hours, falling below, and again becoming ap- 

 proximately normal in about 14 hours, thus 

 showing a series of waves of decreasing mag- 

 nitude and increasing length. 



