62 



T. If. Chatard — TJrao. 



branching coral, each of the branches forming a cylinder, a sec- 

 tion of which shows the radiated structure, while the surface of 

 the cylinder is rough, the curved edges of the crystal aggregates 

 giving a lenticular appearance. The color is brownish and one 

 side of the specimen shows crystals of NaCl and much sand as 

 the evaporation of the water finally left it lying on the mud of 

 the bottom. 



No. 4 or " Lagune" is from another small lagune near by, and 

 consists of a thin sheet, the surfaces of which are rough like the 

 preceding specimen. Color pink, due to organic matter. 



No. 5 or " Beach vat " was formed in a vat dug in the beach 

 and allowed to till by seepage from the surrounding soil. This 

 seepage water differs somewhat in composition from the water 

 of the lake. 







No. 1. 



No. 2. 



No. 3. 



Twig. 



No. 4. 



Lagune. 



No. 5. 

 Beach vat. 



In sol. 



inorg. 



•02 



•22 



2-92 



•40 



4-10 



" oro-anic 











•14 



•12 



•27 



SiO 







•10 



•05 



•09 

 •06 



•04 



CaO_. 







Mo-0 . 

















•02 







K o 0__ 









.... 





tr. 







Na 2 0. 





|40-995 



41-26 



40-22 



40-08 



39-36 



CI.... 





1 -193 



1-57 



2-73 



•21 



1-83 



so 3 ... 





f -702 



•79 



•76 



•63 



•84 



co 2 .. 





| 38-13 



37-00 



35-24 



37-50 



35-10 



HO.. 





| 20-07 



19-62 



18-31 



100-37 



1994 



18-58 











100-11 



100-56 



99-05 



100-12 



0=C1 





•04 



•35 



•61 



•05 



•41 



100-07 100-21 99-76 99-00 99-71 



Calculating the hypothetical composition, deducting the im- 

 purities and recalculating to 100 per cent we have : 



No. 1. No. 2. No. 3. No. 4. No. 5. 



Na 2 C0 3 46-57 47-20 46-76 50-35 46'65 



NaHC0 3 ... 37-03 36-22 37*04 32'53 36'83 



HO 16-40 16-58 16*20 17-12 16*52 



100-00 100-00 100-00 100-00 100-00 



If we compare these new percentages with the theoretical 

 figures for urao, previously given, we shall find the following dif- 

 ferences. 





Theoret. No. 1. 



No. 2. 



No. 3. 



No. 4. 



No. 5. 



Na 2 Co 3 .... 



46-90 --33 



+ •30 



— •14 



+ 3-45 



-•25 



NaHC0 9 _. 



37-17 —-14 



—•95 



-•13 



— 4-64 



—•34 



H 2 



15-93 +'47 



+ •65 



+ 27 



+ 1-19 



+ •59 



