296 Scientific Intelligence. 



the island of Marajo did not exist, and the Amazonas formed an 

 estuary opening widely to the sea. Not only were the lower plains 

 of Para flooded, but immense tracts of the province of Ama- 

 zonas were covered with water. How far this salt water pene- 

 trated I do not know, but the shells of Pebas show that at one 

 time its influence may have extended far up toward the Andes, 

 At the time of the growth of the Santarem shells the water 

 may have been brackish. With the gradual rise of the conti- 

 nent, not of the Andes alone, the fresh waters drove down the 

 salt, the narrow river bed with its numerous channels was hol- 

 lowed out of the emerging bottom, the sea began to attack and 

 cut away the coast lands, and the present estuary condition of 

 the mouths of the great river was brought about. I have not 

 yet told half the story of the history of the Amazonian valley. 

 It is by no means a simple one, and there are more episodes in 

 it than we have hitherto dreamed. The Amazonas is a world, 

 and no one man need hope to exhaust its wonders. 



Cornell University, Ithaca, N. T., Feb. 23d, 1871. 



SCIENTIFIC INTELLIGENCE. 



L Chemistry and Physics. 

 1. On some Zecture-experiments.—{\.) To show the reciprocal 

 combustion of the elements of water, Julius Thomsex proceeds 

 as follows : two narrow tubes of platinum, a centimeter long hy a 

 millimeter in diameter, formed by rolling up a piece of foil, are 

 melted into the ends of two narrow glass tubes, and serve tor tne 

 jets. These glass tubes pass through a rubber cork, distant trom 

 each other about a centimeter. One of them communicates ^ntn 

 an oxygen gas-holder, the other with one containing ^J^^^^f^ 

 The cocks of both are opened, the hydrogen is ignited and tne 

 stopper with its tubes, is introduced into a wide glass tube lu 

 15 centuneters long, slightly constricted at its lower end, a _^ 



narrow opening above. The hydrogen now ouru* u 

 the oxygen, the platinum jets protecting the tubes. It ^^^, 

 oxygen be gradually shut off, a point will be soon reached w 

 the amount present will be insufficient for the combustion of the 

 hydrogen ; the flame expands, and apparently disappears, du 

 an instant re-appears upon the oxygen tube, the oxygen ^^^ ° ^^g 

 ing in hydrogen. On admitting more oxygen theflame P 

 over again to the hydrogen tube as at the' first. This exchange 

 may be repeated as often as is desired without extingaismng^.^j^ 

 flame and without danger, if the oxygen be let on and cut on 

 sufficient slowness. ^ rruom- 



(2.) To show that oxygen may bum with a smoky flame, i^ 

 sen uses the vapor either of turpentine or of benzol Some i^ a. 

 is heated to boiling in a long-necked flask closed with a stopp 



