Sentence:  It is the remark of an ingenious writer, should a barbarous Indian, who had never seen a palace or a ship, view their separate and disjointed parts, and observe the pillars, doors, windows, cornices and turrets of the one, or the prow and stern, the ribs and masts, the ropes and shrouds, the sails and tackle of the other, he would be able to form but a very lame and <WSD>dark</WSD> idea of either of those excellent and useful inventions. 
Meaning of the word marked with <WSD> tags:  Not clear to the understanding; not easily through; obscure; mysterious; hidden.