TO THE LIBRARIAN OF THE ROYAL SOCIETY.

                                                             Glenlair, Dalbeattie, 23d June 1879.

     DEAR SIR—Your information about F.R.S. has been so useful to me that I now ask about Dr. G. Knight,    F.R.S., librarian to the British Museum.

(1.) Is his name Gowan, Gowen, Gowin, or Godwin, for I find all four spellings current?

(2.) Who is the author of the paper in Phil. Trans. for 1776 (near the end of the vol.)  describing his great  magazines of magnets?

(3.) Are the magazines [sketch shown] mounted like great guns still in the possession of the R.S.?

(4.) Is the portrait of Gowin Knight, by Benjamin Wilson, F.R.S., among the pictures of the  R..S.?

     I have got from the Meteorological Office some Cavendish MSS. on Magnetism which prompt these enquiries    and also this—-

 When the R. S. was at Crane Court had it a garden adjoining? Also, where was Crane Court?

 Henry Cavendish and his father Lord Charles worked together at observations of the variation compass and    dipping  needle in the R. S. room and garden. Are the variation compass and dipping needle still in the R. S.   collection?

     Cavendish wrote out directions for using the dipping needle for Captain Pickersgill, Captain Bayley, Dalrymple.

     Dalrymple, I find from Poggendorff, was hydrographer to the H.E.I.C. If Cavendish apportioned his instructions    according to the capacity of the recipients, then their capacities would be in descending order, Dalrymple,    Pickersgill, Bayley. Were any of these F.R.S. ?

     Also, was John Walsh, F.R.S., also M.P.?

     Do not answer any of these questions which would involve trouble, but I have not here any means of answering    them except by the aid of those who are among the records of the past. None of the questions are of vital   importance, because I can leave out any statements I have made which are doubtful. Yours very truly,—

                                                                        J. CLERK MAXWELL.