430 E. W. Hilyard— Geology of the Delta, 



1. There is a general similarity of composition between the 

 waters of the mudlump springs, indicating their derivation from 

 a common source of supply. But springs on the same lump, as 



Their density is generally inferior to that of sea-water, thouirli 

 at times approaching it closely. 



2. There is an obvious approximation of the ratio between 

 the two chief bases — sodium and magnesium — to that existing 

 in sea- water ; the variations being no greater than are observed 

 in sea-water from different localities. 



8. The most obvious difference is the absence of sulphates, 

 and their partial replacement by chlorides : also 



4. Tlie presence of large amounts of the carbonates of the 

 earths, as well as of iron, dissolved in carbonic acid. 



6. The amount of potassium salts is decidedly diminished. 



6. Bromids appear to be entirelv absent, and are present in 

 traces only, in the water of the Gulf itself 



It is stated that the waters of some of the springs are fresh. 

 I have found all brackish at least, and as the population of the 

 delta is much in the habit of drinking water of questionable 

 freshness, their judgment in the matter may not be the most re- 

 liable. 



As regards the water of the New Orieans well, though at tii'st 

 sight it differs materially from the others, it will be observed 

 that when in C, potassmm and sodium chlorides arc classe.l 

 together, its composition becomes not unlike the mudlump wa- 

 ters. Its great dilution accounts for the excessive proportion ot 

 carbonates. 



The Gulf water approaches very closely in its composition 

 to the normal one of sea-water, as given by Eegnault. 



Mud from Mudlump Springs. — I have already stated, that the 

 stratified material of the mudlumps (whether formed by the ac- 

 tion of mud springs, or bodily upheaved) is free from visible 

 shells or other fossils, save particles of woody matter ; while 

 the amorphous material which forms the surface and generally 

 also the beach, often abounds in such organic remains as are 

 now usually washed ashore, having manifestly been cast up and 

 imbedded in the mud by the waves. 



I have examined microscopically the mud remaining i^^^^ 

 specimen bottles after decanting the water for analysis; thev 

 were immediately refilled with distilled water, and kept 

 closely stopped until examined. I give below the record ot 

 examination of the mud, corresponding to analysis Ko. \ • 

 from West Crater on Marindin's Lump. Two or three otber= 

 similarly examined gave a like result. 



