No time to write. Have had hither to put off accounts because Farquhar leaves the 15th. Experiments finished at Kew. They appear to be very fine. Thus, length of pendulum on four days agrees to 1/10000 millimeter. Now remains to fix accounts, scrutinize records  & make (…) to see all is satisfactory, & to make some comparisons of standard in Berlin which they weren't before ready for. I go there for a few days shall leave tomorrow. Shall do accounts first thing. As to classification of vids [?], I have attempted something in my Logic of Relatives. I fear it is not very satisfactory however. As to the fourth unit of quaternions I had some remarks which you cut out of my paper in printing it. An absurdity wanted for greater freedom! Am well & Z too. Love in torrents to all Jem especially.