"I was delighted to find that she had been an intimate friend of Mrs. Somerville; had corresponded with her for years, and had a letter from her after she was ninety-two years of age, when she was reading Quaternions for amusement.

Four N. quaternity^, four, tetrad, quartet, quaternion, square, quarter.

Up to this time, it had been the fixed assumption of the four inside people, (as an old tradition of all public carriages from the reign of Charles II.,) that they, the illustrious quaternion, constituted a porcelain variety of the human race, whose dignity would have been compromised by exchanging one word of civility with the three miserable delf ware outsides.

But we would maintain, nevertheless, that it is the identical book, and explain this variation in the description by the circumstance that the library having, in the space of nearly two centuries, been materially enriched, numerous works, consisting in many cases only of a single "quaternion," were inserted in the volumes already existing.

[Footnote 8: A leaf is here torn out of the first quaternion of the Medicean MS.

because the first leaf in the third quaternion is lacking.

It is not right to say, "Three times one quaternion is twelve;" nor is it quite unobjectionable to say, with Blanchard "3 times the number 4, is the number 12."

Again, the science of quaternions, or more generally, a vector analysis in which the progress of electrical science is essentially involved, embraces (explicitly or implicitly) the extensive use of imaginary or impossible quantities of the earlier algebraists.

He was the discoverer of a new calculus, that of Quaternions, which attracted the attention of Professor Tait of Edinburgh, and was by him made comprehensible to lesser mathematicians.

A page of quaternions gives me more pleasure than all this rubbish put together, though I am not averse to a little gossip now and then of an evening, if people will listen to my details and fancies.