This method of approach to the quaternion vector analysis is practically that adopted by Prof. Joly in his “Manual of Quaternions.” The method is unsatisfactory, because it makes too great a demand at ...

IN a paper by Prof. C. G. Knott on “Recent Innovations in Vector Theory,” of which an abstract has been given in NATURE (vol. xlvii. pp. 590–593; see also a minor abstract on p. 287), the doctrine ...