Hints on Levelling Operations, as Applied to the Reading of Distances by the Law of Perspective, and the Saving Thereby of Chainmen in a Level Survey: With Remarks on the Other Advantages That Can Be Gained in a Survey by Adopting This Principle in the Us: Buy Hints on Levelling Operations, as Applied to the Reading of Distances by the Law of Perspective, and the Saving Thereby of Chainmen in a Level Survey: With Remarks on the Other Advantages That Can Be Gained in a Survey by Adopting This Principle in the Us by Wells W. H. at Low Price in India