The great probability of a north west passage : deduced from observations on the letter of admiral De Fonte, who failed from the Callao of Lima on the discovery of a communication between the south sea and the atlantic ocean. / Thomas Jefferys . .. Proving the authenticity of the admiral's letter. With three explanatory maps... By thomas Jefferys... with the account of a doscovery of part of the coast and inland country of Labrador, made in 1753. The whole intended for the advancement of trade and commerce