Howe and Campbell — Specimens from Yticatan. 415 



Qualitative examination showed results similar to those of 

 the water 172 taken near the shore. While the two waters 

 resemble each other as regards the salts present, it will be 

 noted that the shore water contains decidedly more calcium 

 sulphate, but less sodium. The presence of hydrogen sulphide 

 in the water from the middle of the lake is difficult to account 

 for, unless there may be a sulphur spring beneath the lake at 

 this point. The shores of the lake being so largely gypsum, as 

 appears from the specimens, the water near the shore might 

 take up more of this material, accounting for the increased 

 gypsum content of the shore water over that of the middle of 

 the lake. 



The gypsum of the lake shore is quite possibly formed from 

 the evaporated lake water. This appears probable from the 

 fact that the gypsum, deposited on evaporating both waters, 

 contains in addition to the ordinary forms a small proportion 

 of crystals similar to those described above in deposit No. 9. 

 If this is the case it would be interesting to know the origin of 

 the large content of gypsum in the lake water. The shore 

 water is evidently a supersaturated solution of gypsum. On 

 the other hand, the lake may obtain its gypsum from the 

 gypsum deposits of the vicinity. The problem must be con- 

 sidered unsolved until further explorations of the lake are 

 made. 



Washington and Lee University, Lexington, Ya., June, 1896. 



Am. Jour. Soi. — Fourth Series, Yol. II, No. 12. — December, 1896 

 30 



