1869-71-] MANYUEMA. 415 



is not always the best symbol for a man out of his 

 element. There were fish too that burrowed in the 

 earth ; but most remarkable at first sight were the fish 

 that appeared to bring forth their young by ejecting them 

 from their mouths. If Bruce or Du Chaillu had made 

 such a statement, remarks Professor Owen, what ridicule 

 would they not have encountered ! But Livingstone was 

 not the man to make a statement of what he had not 

 ascertained, or to be content until he had found a scientific 

 explanation of it. He found that in the branchial open- 

 ings of the fish, there occur bags or pouches, on the same 

 principle as the pouch of the opossum, where the young 

 may be lodged for a time for protection or nourishment, 

 and that when the creatures are discharged through the 

 mouth into the water, it is only from a temporary cradle 

 where they were probably enjoying repose, beyond the 

 reach of enemies. 



Perhaps the greatest of Livingstone's scientific dis- 

 coveries during this journey was that "of a physical 

 condition of the earth's surface in elevated tracts of the 

 great continent, unknown before." The bogs or earth- 

 sponges, that from his first acquaintance with them gave 

 him so much trouble, and at last proved the occasion of 

 his death, were not only remarkable in themselves, but 

 interesting as probably explaining the annual inundations 

 of most of the rivers. Wherever there was a plain sloping 

 towards a narrow opening in hills or higher ground, there 

 were the conditions for an African sponge. The vegeta- 

 tion falls down and rots, and forms a rich black loam, 

 resting often, two or three feet thick, on a bed of pure 

 river sand. The early rains turn the vegetation into slush, 

 and fill the pools. The later rains, finding the pools 

 already full, run off to the rivers, and form the inundation. 

 The first rains occur south of the equator when the sun 

 goes vertically over any spot, and the second or greater 

 rains happen in his course north again. This, certainly, 



