Geology and Mineralogy. 463 



an error in my article on the Mechanical Properties of Catgut 

 Musical Strings, which appeared in the last issue of this Journal. 

 On page 384, under the heading "Hygroscopic Properties," some 

 observations are discussed which appear to show that the string 

 in question increased in length with increasing humidity ; 

 although, as mentioned there, its behavior was much complicated 

 by after- effects. It is well known that the catgut strings of 

 musical instruments are affected by changes of humidity : but 

 they tend to contract with increasing humidity, and not to stretch, 

 as stated in the article. The string on which I made observa- 

 tions showed just the opposite behavior ; but it was under dif- 

 ferent conditions from the strings in musical instruments. In 

 the first place, it was under far less tension ; in the second place, 

 it was free from any torsion ; consequently any lateral swelling 

 of its fibers which might occur would have no tendency to shorten 

 it, while such swelling would tend to shorten a twisted string. 



II. Geology and Mineralogy. 



1. Iowa Geological Survey, Volume XK Annual Report, 

 190 Jf, with accompanying papers. Frank A. Wilder, State 

 Geologist ; T. E. Savage, Assistant Geologist. Pp. viii, 560, 7 

 plates, 51 figures and 10 geological maps. Des Moines, 1905. — 

 The Geological Survey of Iowa, under the charge of Professor 

 Samuel Calvin, has enjoyed an excellent reputation for the thor- 

 ough and systematic work which it has accomplished since its 

 inauguration. Professor Calvin has now found it necessary to 

 resign from the position of chief responsibility, and the place has 

 been filled by Professor Frank A. Wilder, under whose auspices 

 the present volume has been published. This volume gives 

 promise that the future work done for the State will be carried 

 forward on the same lines and with the same excellent results 

 that have characterized its predecessors. 



The volume contains, in addition to the administrative report, 

 a chapter on the Mineral Production in 1904, by S. W. Beyer ; 

 another on Cement and Cement Material, by E. C. Eckel and H. 

 F. Bain ; and then a series of chapters discussing in detail the 

 geolog}'' of a number of counties accompanied by geological maps. 

 These special reports include the following: On the Geology of 

 Benton County, by T. E. Savage ; of Emmet, Palo Alto and 

 Pocahontas Counties, by Thomas H. Macbride ; of Jasper County, 

 by Ira A. Williams ; of Clinton County, by Jon Andreas Udden; 

 of Fayette County, by T. E. Savage. It is stated that the field 

 work for 1905 is being carried on preeminently along economic 

 lines, the earlier stratigraphic work having laid the necessary 

 foundation. 



In the report of Mr. Beyer alluded to above, it is shown that 

 the value of the mineral productions of the State in 1904 was 



