These are copies in an unknown hand [the name "Meriel Nevill Watt" appears in the front of the volume] of letters, primarily from Ellis, that were published in the "Philosophical Transactions" of the Royal Society in London. Most relate to botanical topics, and many are written to Peter Collinson. A few are written by Peter Woulfe. Included are contemporary engravings from the "Transactions," as well as original wash drawings copied from the engravings.

This treatise includes experiments on eletricity (with mentions of B. Franklin), ballooning (mentions of J. P. Blanchard), pharmacology, chemistr, and hydraulics. Included is a sketch of Woulfe's bottle for passing gases through liquids (Peter Woulfe, 1767).