Question

where the clear stream of reason has not lost its way meaning of this sentence

Answer 1

where there are no superstitions
the desert here are the superstitions followed by people which usually doesnt have any logic or reason. here Rabindranath Tagore, the writer, talks about a place where there are no illogical superstitions followed

Answer 2

the place, the things, or work consequences of whose is clearly known...