60 H. S. Car hart — One- Volt Standard Cell. 



portion of the county we find both. On west side of St. 

 Francois Eiver not far from mouth of Leatherwood Creek the 

 section shows : 



1-4 feet Magnesian limestone. 



2-4 feet Gritstone. 



3-9 feet of Magnesian limestone. 



4-3 feet of Gritstone. 



5-11 feet of Magnesian limestone. 



6-20 feet of Marble beds. 



On Twelve Creek I have found the Gritstone beds resting 

 on the marble which in turn rests upon the porphyry. In 

 this way I obtained my general section of Madison County as 

 above. On Marble Creek in Iron County the Magnesian lime- 

 stones are seen resting directly upon the porphyry. 



The sandstone and the Marble beds not being persistent are 

 found at some places resting upon the porphyry or granite 

 (Archaean) at other places the limestones rest directly upon 

 the Archaean. The upper beds of the Ozark Series are in the 

 main persistent. Near Augusta the regular succession, from 

 first Magnesian to second Magnesian is preserved. At Crystal 

 City, Pacific and Westpoint, 111., the two upper members are 

 well exposed. On the Gasconade and Osage the second and 

 third Magnesian limestones with the separating and incumbent 

 sandstones are well marked. So, taking all the evidence in 

 the case one had better go very slow before he attempts a new 

 arrangement or classification. 



Art. IX. — A One - Volt Standard Cell ; by 

 Henry S. Carhart. 



[Read before the National Academy of Sciences, Washington, April 21, 1893.] 



The calomel cell, consisting of mercury in contact with mer- 

 curous chloride and zinc in a solution of zinc chloride, was first 

 described by von Helmholtz in 1882.* Without any knowledge 

 of its previous invention I made the same cell six years ago 

 and have still the first sample made at that time. Ostwaldf 

 refers to a calomel cell giving one volt E. M. F. at 15° C, the 

 density of the zinc chloride being 1409 at 15°, and the tem- 

 perature coefficient -f '00007 volt per degree. 



Within the last few months I have taken up the calomel cell 

 again with a view of adjusting it to precisely one volt, making 

 a careful determination of its temperature coefficient, and in- 

 vestigating its reliability. 



* Sitzber. der Akad. der Wiss., p. 26, Berlin, 1882. 

 f Zeitschrift fur Physikalische Chemie, vol. i, p. 403. 



