Howe and Camjpbell — Specimens from Yucatan. 413 



Akt. LYIII. — Examination of Specimens from Chicham.- 

 Kanab, Yucatan / by Jas. Lewis Howe and H. D. 

 Campbell. 



In 1894 Mr. E. H. Thompson of Merida, Yucatan, in con- 

 nection with his archaeological researches, collected and for- 

 warded to Prof. F. W. Putnam specimens of water and earth 

 deposits from "the Chichan-Kanab (little sea), an almost 

 unknown lake over six leagues long situated far into the terri- 

 tory of the Sublemdo Indians" in the peninsula of Yucatan. 

 These specimens were placed by Prof. Putnam in the hands of 

 one of us for examination ; they were as follows : 



'' Wo. 8. Specimen of incrustation found twenty yards from 

 present lake edge March 6, 1894." 



" Wo. 9. Encountered one foot beneath alluvium deposit 

 half league from foot of Lake Chichan-Kanab." 



" Spec. 17'2. Water taken from one yard off shore upper end 

 Chichan-Kanab." 



" Spec. 1189. Water taken off middle of Lake Chichan- 

 Kanab, State of Yucatan, Mexico." 



No. 8 was a light buff crystalline mass which on analysis 

 proved to be gypsum. 



No. 9 was a light gray mass resembling dried mud. It was 

 easily friable and could be rubbed in the fingers to a fine 

 powder. This like No. 8 was almost pure gypsum, a small 

 amount of vegetable matter being present. A portion was 

 dissolved in water and two equal portions of the solution 

 analysed, one for calcium and the other for sulphuric acid. 

 0*0260 grams calcium and 0*0612 grams SO^ were found. The 

 formula CaSO^ would require 0*0255 grams calcium for 0*0612 

 grams SO^. Two grams of the material lost on 22 hours heating 

 at 160° 0-4083 grams or 20*42 per cent. At red heat the total 

 loss was 0*4323 grams or 21*62 per cent. The percentage of 

 water in gypsum is 20*93 per cent. Under the microscope 

 the powder was seen to consist of small crystals. 



Regarding this gypsum. Prof. H. D. Campbell reports as 

 follows : The powder consists of lenticular crystals, not rounded 

 grains nor crystal aggregates, nor as far as observed is 

 twinning shown. The largest crystals have a diameter of 0*15*""^ 

 and a thickness .of 0*06™°". The smallest ones still appear as 

 powder under the higher powers of the microscope. The 

 crystals show a more or less hexagonal outline, indicating the 

 presence of prismatic and clinopinacoidal faces. Curved faces 

 run up toward a point and appear to represent the faces of 

 pyramid and dome. When dissolved in water and recrystal- 

 lized, they assume the more usual forms of gypsum crystals. 



