I received yours of the 23d of April as I was going on board the sloop in my return home from New York and could not take the pleasure of reading it before I left that place.

One so much conversant in examining any particular Phoenomenon or of various Phoenomena arising from the same cause must on every occasion give the pleasure of learning something new to those less conversant in them as often as the first is pleased to answer any objections of the latter or explain the diversities or variations which attend the same phoenomenon in different cases or appearances.

Your conjecture of the Electric fluid’s taking place in the superior regions of our atmosphere pleases my fancy as it in some measure confirms what I have advanced in the Treatise now in the press viz. That all the Planets in a greater or less degree emit Light and indeed I think that all bodies do. It does not follow that because we do not see the light that none is emitted. Some men can see where others are entirely in the Dark and some Animals as Owls, Batts, &c. see in the Dark and cannot bear so great a degree of Light as is necessary for our Perceptions.

When you shall see that Tract you will have opportunity of Judgeing of the Validity of the reasons I advance for an opinion that Light is a substance or Being essentially distinct from what we commonly call Matter or Body; that they have nothing in common between them except that we consider or conceive both as consisting of Quantity, that is, that in the same space there may be a greater or less quantity of either and that a certain quantity of either may be confined within certain bounds and consequently have some shape or form. Light has no power of attraction though it be attracted by resisting matter.

The Vibrations of a Fluid will in no manner explain the Phoenomena of Light as is very expressly pointed out in Sir Isaac Newtone’s optics; for example, Light proceeds allwise in streight lines unless diverted by some other thing. For this reason any opac body placed between the eye and a luminous body intercepts all the light but it does not intercept the sound coming from a sonorous body because Sound is conveyed by the Vibrations of a fluid Medium not by any emission of particles from the sounding body. Again the seperation of the distinct parts of Light which excite in us the different and distinct sensations of colours and which once seperated allwise remain the same prove that these sensations can not be produced by the Vibrations of any Medium supposed to convey the Action of Light from the Luminous body. I am persuaded that a carefull attention to the Phoenomena in Sir Isaacs optics and to his reflections on them will remove all doubt on this head.

On this occasion I think it proper to observe to you that in the Treatise before mentioned what Sir Isaac has proved is generally taken for granted and supposed to be known.

It may be proper likewise to observe to you that pure Light without any other mixture makes no impression on any other sense except the Sight. That the sense of heat arises from the Action of Light united with the action of some resisting matter. So likewise we have no Idea of fire without the union of resisting matter with Light.

In considering all Quantities or Degrees of Action or Force whether in ascending or descending, whether in considering them as continually increasing or continually decreasing, the ratio of comparison must at last come to that of infinity. We have no Idea of the absolute Force of any thing, only of its comparative force—or ratio of its force—to that of some other thing. The force of Different quantities of Light does not arise from the different Velocities (for I suppose all light allwise moves in the same ratio of Velocity Compared with any velocity that can be distinguished by our senses) but from the greater quantity or density of Light in the same Space.

If the emission of Light be not continued but by distinct vibrations or pulses and an infinitely thin surface of Light be thrown off in any finite part of time, suppose in a fifth, then there cannot be any finite or determinable diminution of the Light of the Sun or of the Diameter of Light in the sun in any finite time. If the intervals of the vibrations or emissions of infinitely thin Surfaces of Light be in an infinitely small part of time, It may take a hundred or a thousand years to diminish the suns Diameter one Inch. You will find something of these abstracted Speculations in the treatise I mention.

I have much reason to apprehend the errors of the press when I reflect on the manner the Indian History has been printed: Such gross errors in things obvious to the meanest understanding. Mr. Dodsley promised to get some person of Learning to correct the Press. Perhaps the Diffculties he meets with in this is the reason that the impression was not compleated in the beginning of March though begun in December.

I shall be exceedingly disapointed if it do not meet with censure. I have laid my account with it Not only with unjust and injurious censure but that many errors may truely be discovered and that it will require much correction. It is impossible to avoid errors in things of this nature more especially in a path not trod in before and where I had no body to assist me to review and examine the work. A Difficulty an author cannot labour under in England.

I have received a Copy of the Translation of my first piece into High Dutch with Animadversions on it at the end of it printed at Hambourg and Leipsic 1748 but I do not understand one word of them.5 I find my name often in company with those of very great ones Newtone, Leibnitz, and Wolfius and Leibnitz’s Monades often mentioned a New Doctrine which perhaps you have seen and is of great repute in Germany. The animadversions end—Magnis tamen excidit ausis6 which being in Latin I understand.

The person in the Boston paper who wants a fuller description of the Poke weed or Phytolacca than that given in the Magazine must have but little skill in Botany for I am confident the Discription is sufficient for a Botanist to distinguish it from any other Plant whatsoever. I know that some people have thought that the Pokeweed is Mechoacan but they who think so know litle of Plants.