T. N. Dale — Plicated Cleavage-Foliation. 



317 



aged on the oxides for the amounts of barium and strontium 

 nitrates taken in order that they may be compared more con- 

 veniently with the results of the previous series. 







Series IV. 









Ba(N0 3 ) 2 



and Sr(N0 3 ) 2 



taken. 



Ba(N0 3 ) 2 

 and Sr(N0 3 ) 

 found and 



corrected. 



2 Error 

 in 

 nitrates. 



Error 

 averaged and 

 calculated as 

 oxide. 



CaO 



taken. 



CaO 

 found. 



Error. 



grams. 



- grams. 



grams. 



grams. 



grams. 



grams. 



grams. 



(17) 0-3941 



0-3945 



0004 + 



0002 + 



0-0283 



0-0277 



0-0006 — 



(18) 0-1436 



0-1442 



0-0006 + 



0-0003 + 



0-0568 



0-0558 



o-ooio- 



(19) 0-3163 



0-3152 



00011- 



0006 — 



0-0284 



0-0274 



o-ooio- 



(20) 0-1978 



0-1987 



0-0009 + 



0-0005 + 



0-0285 



0-0280 



0-0005- 



(21) 0-1948 



01932 



00016- 



0-0008- 



0-0833 



0-0835 



00002 + 



(22) 0-1971 



01971 



o-oooo 



0-0000 



0-0830 



0-0817 



0-0013 — 



(23) 0-1973 



0-1960 



0-0013 — 



0-0007- 



0-0830 



0-0824 



0-0006- 



(24) 0-1959 



0-1970 



0-0011 + 



0-0005 + 



0-0830 



0-0S19 



o-ooii— 



(25) 0-1971 



0-1963 



0-0008 + 



0-0004 + 



0-0834 



0-0831 



0-0003 — 



In experiments (21), (25) 15cm 3 of the alcohol were used in 

 each boiling instead of the 30cm 3 of the previous experiments, 

 and thus the total amount of the corrections for the solubility 

 of the strontium salt was reduced one-half. In experiments 

 (21), (23) and (25) tlie calcium was determined by precipitation 

 with sulphuric acid, the precipitate being filtered off, ignited at 

 low redness and weighed.' 



The rapidity of execution and satisfactory character of the 

 results of this method of separating barium from calcium seem 

 to place it among good analytical methods. 



Art. XXXVIII. — On Plicated Cleavage-Foliation / by 

 T. Nelson Dale. 



[Published by permission of the Director of the TJ. S. Geological Survey.] 



The schists and slates of the Taconic Range in Western 

 Massachusetts and Vermont aiford a good field for studying 

 the various phases of cleavage : slaty-cleavage, slip-cleavage,* 

 close-joint-cleavage. Some of the results of such a study have 

 been published in outline by the writer, f and others are in 

 course of preparation. 



De la Beche^;, and later Charles Darwin§ noticed that the 

 upturned cleavage laminae of clay-slate were sometimes curved 

 at the surface, and Dr. Hans Reusch of Christiania|| cites an 



* " Ausweichungs-clivage " of Heim; " strain-slip cleavage " of Bomiey. 

 •{•The G-reylock Synclinorium. American Geologist, July, 1891. 

 j Geological Manual, p. 42, 1831. 



§ Geological Observations on Coral Reefs, Volcanic Islands and on South 

 America, Part III, p. 160, London, 1851. 



|| Bommel^en og Komm^en med omgivelser, p. 196, Kristiania, 1888. 



