xin.] ON THE KAPUAS LAKES 



Although rains are torrential and continuous, the waters of 

 the rivers in Borneo rarely get turbid, because the amount of soil 

 not covered with vegetation, or cultivated, whence earthy matter 

 can be carried off, is of small extent. Rain, however violent, is in 

 a country covered by forest obliged to filter through great masses 

 of vegetation, and comes gently to the ground, where, again, it 

 meets a thick layer of dead leaves, rapidly decomposing under the 

 influence of heat and moisture and the development of myriads 

 of micro-organisms. The water, therefore, when it collects in streams 

 is poor in earthy deposits, having been filtered through this vast 

 stratum of decomposing vegetable matter ; and when the waters 

 of these streams rise and inundate the forest, they absorb various 

 new substances. Amongst these, humic acid predominates, and 

 it contributes more than anything else to produce the peculiar 

 dark coloration. It is not everywhere, however, even under the 

 circumstances above mentioned, that the waters retain their black 

 colour. This only happens when they do not contain lime. In 

 South American rivers it has been observed that when the dark 

 waters mingle with white waters they at once lose their colour, 

 through a reaction of the humic acid on the lime. I believe that 

 the same thing takes place in Borneo, but I have no direct observa- 

 tions on the subject. 



As we approached the lakes the Umpanang increased in width ; 

 but, strange to say, the trees diminished in height, getting so low 

 as to be not more than from ten to twenty feet above the water. 

 But what surprises one most on entering the lake from the river 

 is the very unusual colour of the great sheet of water before us. 

 Looking straight down into its depths it appears so intensely black 

 as to cause a certain sensation of fear. At times I felt as if the 

 boat must sink in that unfathomable dark abyss ! Our ideas on 

 the specific gravity of water are naturally associated with the 

 coloration which is familiar to us. They might be termed 

 innate ideas ; and even a child shows no surprise that a boat floats. 

 But when waters show a coloration so different from the ordinary, 

 even the notion one possesses instinctively of its specific gravity is 

 shaken. These inky waters certainly do not tempt one to a plunge ; 

 whilst, as all know, the opposite feeling is elicited by limpid and 

 transparent water, the mere sight alone of which is always pleasant 

 and attractive. 



The surface of the lake, clear and free from arboreal vegetation, 

 extends only a few miles, but nowhere could we see a trace of dry 

 land. As soon as we issued from the Umpanang, we sighted Lamadan. 

 a village inhabited by Malays, towards which we proceeded. My 

 people called the lake Danau Lamadjan, 1 but I believe that it is 

 better known to the Kapuas people as Danau Seriang. 

 1 Dapau is the Malay for lake. — Ed. 

 l83 



