THE MUSEUM. 



205 



some six or eight inches above the 

 water level and were about i 5 inches 

 across; the water was about 12 or 15 

 inches deep. None of these nests as 

 yet contained eggs; and although I re- 

 turned to the "pajarera" on the latest 

 day I was in this neighborhood (May 

 11) they still remained empty. On 

 both occasions many Flamingoes were 

 sitting on the nests, and on the iith 

 we had a good view of them at close 

 quarters. Linked arm and arm with 

 Felipe, and crouched low on the 

 water to look as little human as pos- 

 sible, we crept within some 70 yards 

 before their sentries showed signs of 

 alarm, and at that distance with the 

 glass, observed the setting birds as 

 distinctly as we need wish. Their 

 long red legs doubled under their 

 bodies, the knees projecting as far as, 

 or beyond the tail, and their graceful 

 necks neatly curled away among their 

 black feathers like a setting swan, 

 with their heads resting on their 

 breasts, and all these points were un- 

 mistakable. Indeed it is hardly neces- 

 ■sary to point out that in the great 

 majority of cases (the nests being hard- 

 ly raised above the level of the flat 

 mud) no other position was possible." 

 "Still none of the crowded nests con- 

 tained a single egg. How strange it 

 is that the Flamingo, a bird that never 

 seems happy unless up to its knees in 

 the water should so long delay the 

 period of incubation; for before eggs 

 could be hatched in these nests and 

 young reared, the water would have 

 entirely disappeared, and the Flamin- 

 goes would be left stranded in the 

 midst of the scorching plain of sun- 

 baked mud. Being unable to return 

 to the marisma I sent Felipe back 

 there on the 26th of May, when he ob- 



tained the eggs. In 1872 I 



obtained eggs taken on the 24th of 

 May. One of my specimens is ex- 

 tremely rugose." 



Asphaltum and the Pitch Lake of 

 Trinidad- 



Although asphaltum, or mixed pitch, 

 is not, like the closely related mineral 

 coal, one of the great agents of mod- 

 ern civilization, its uses in the arts 

 are varied and important. The pop- 

 ular knowledge of its nature and ori- 

 gin, however, is limited and imperfect. 

 Asphaltum is one of many native bi- 

 tumens; and among these bodies we 

 observe a graduation from the solid 

 asphalum, through intermediate forms, 

 known as miineral tar, to liquid petro- 

 leum and limpid naphtha. It has 

 been definitely settled, that, in their 

 origins, the bitumens are organic, be- 

 ing transformed tissues of plants and 

 animals. 



Chemically considered, the bitu- 

 mens, like the coals, are hydrocar- 

 bons, but differ in containing little or 

 no oxygen, and a much larger propor- 

 tion of hydrogen. The influence of 

 this extremely fluid element is very 

 evident; for, while the coals agree in 

 being infusible and insoluble, the bi- 

 tumens are either naturally liquid, or 

 become liquid when heated, are solu- 

 ble in benzole, ether, etc. 



Modern investigations, however, 

 have made it certain, that, in their 

 origin, the bitumens are more varied 

 than the coals. Coal is due to the 

 accumulation of half decayed land 

 plants in the waters of swamps and 

 marshes; but geologists are now well 

 agreed that the lighter and more fluid 

 bitumens, like petroleum are mainly 

 marine, being derived partly from sea- 



