They have never been published.

Nevertheless, we can gather what they were.
Cook, in the published account of his Second Voyage, says he had instructions to proceed directly to Tahiti, and afterwards to prosecute the design of making discoveries in the Pacific by proceeding southward to the latitude of 40 degrees, and if he did not find land to continue his voyage to the west till he fell in with New Zealand, which he was directed to explore, and thence to return to England by such route as he should judge most convenient.
Precautions against the terrible scourge, scurvy, had not been forgotten.
Besides the supply of all anti-scorbutics then known, a special letter was written to Cook directing him to take a quantity of malt to sea, for the purpose of being made into wort, as a cure for scorbutic disorders, as recommended by Dr.McBride.
The directions for its use were as follows:-- "The malt must be ground under the direction of the surgeon, and made into wort, fresh every day, in the following manner:-- "1.

Take one quart of ground malt, and pour on it three quarts of boiling water.

Stir them well, and let the mixture stand close covered up for three or four hours, after which strain off the liquor.
"2.

The wort, so prepared, is then to be boiled into a panada, with sea biscuit or dried fruits generally carried to sea.
"3.