The English works of Thomas Hobbes of Malmesbury, Volume 07 (of 11)
Thomas Hobbes · en
Let the first series be of three terms subscribed with the greatest (0.
1. 8.)/(8. 8. 8.); the sum of the cubes is nine; the sum of all the
greatest is 24; a quarter whereof is 6. But 9 is greater than 6 by three
unities. An unity is something. Let it be therefore A. Therefore the row
of cubes is greater than a quarter of three times eight, by three A.
Again, let the series have four terms, as (0. 1. 8. 27)/(27. 27. 27.
27); the sum of the cubes is 36; a quarter of the sum of all the
greatest is twenty-seven. But thirty-six is greater than twenty-seven by
nine, that is, by 9 A. The excess therefore of the sum of the cubes
above the fourth part of the sum of all the greatest, is increased by
the increase of the number of terms. Again, let the terms be five, as
(0. 1. 8. 27. 64)/(64. 64. 64. 64. 64), the sum of the cubes is one
hundred; the sum of all the greatest three hundred and twenty; a quarter
whereof is eighty. But one hundred is greater than eighty by twenty,
that is, by 20 A. So you see that this lemma also is false. And yet
there is grounded upon it all that which you have of comparing parabolas
and paraboloeides with the parallelograms wherein they are accommodated.
And therefore though it be true, that the parabola is (2)/(3) and the
cubical paraboloeides (3)/(4) of their parallelograms respectively, yet
it is more than you were certain of when you referred me, for the
learning of geometry, to this book of yours. Besides, any man may
perceive that without these two lemmas (which are mingled with all your
compounded series with their excesses) there is nothing demonstrated to
the end of your book: which to prosecute particularly, were but a vain
expense of time. Truly, were it not that I must defend my reputation, I
should not have showed the world how little there is of sound doctrine
in any of your books. For when I think how dejected you will be for the
future, and how the grief of so much time irrecoverably lost, together
with the conscience of taking so great a stipend, for mis-teaching the
young men of the University, and the consideration of how much your
friends will be ashamed of you, will accompany you for the rest of your
life, I have more compassion for you than you have deserved. Your
treatise of the _Angle of Contact_ , I have before confuted in a very
few leaves. And for that of your _Conic Sections_ , it is so covered
over with the scab of symbols, that I had not the patience to examine
whether it be well or ill demonstrated.
Yet I observed thus much, that you find a tangent to a point given in
the section by a diameter given; and in the next chapter after, you
teach the finding of a diameter, which is not artificially done.