I have been honored with your favour of the 22d Ult. and feel, with a lively sense, the obligation I am under for the interest you were pleased to take in behalf of my friend, though the appointment has fallen on another worthy gentleman of the same name. I am not a little flattered with the notice you have taken of my cypher—Your alteration will certainly very much facilitate the labour of the Principal, without greatly increasing that of the copyist. There is yet another alteration, relative to the Key, which, I conceive, would be of considerable advantage—Instead of expressing it by figures, which are so liable to be forgotten, it may be expressed by a single word or name, which may always be remembred, without committing it to writing. For example, suppose the key-word Montecello—the letters of this word are to be numbered according to their place in the alphabet, any letter repeated, being referred to a second, or third alphabet—thus the letters in the above word be numbered as follows

M	o	n	t	e	c	e	l	l	o
4,	6,	5,	7,	2,	1,	8,	3,	9,	10.

the second e, l, and o being referred to a second alphabet, and according numbered 8, 9, 10. This key-word will then signify that there are ten vertical lines in the section, which are to be transcribed, in horizontal lines in the order of the above figures viz. 4th. 6th. 5th. &c The same word may also be used to signify the number of supplementary or insignificant letters at the beginning of the respective lines, as 4 at the beginning of the first, 6, at that of the second &c Or two key-words may be used; the first to signify the number and order of lines in the section, and the second, the supplementary letters. When the two words do not consist of an equal number of letters, then so many of the first letters of the least word may be subjoined to the end of it, as to make their number equal—Thus James Maddison, as a key, would be written and numbered in this manner

J	a	m	e	s	j	a	m	M	a	d	d	i	s	o	n
3,	1,	4,	2,	5,	7,	6,	8;	4,	1,	2,	8,	3,	7,	6,	5.

There is but one wooden Sextant, that I can find, to be disposed of at present in this city. It is a very good one—with telescopes, tangent and adjusting screws, and every other appendage complete—the price 45 dollars. A stand might be made for it at no great expense. A very little practice, however, would render the use of the instrument, both in measuring vertical and horizontal angles, without a stand, as easy as with one. The Thermometers are ready, but as I have not yet seen or heard from Mr. Barnes, I must request you to send me such further directions, relative to the purchase of the sextant, and sending on the instruments, as you may think proper

An experiment which Mr. Raphael Peale lately exhibited before a number of citizens, at the Coffeehouse, has excited a good deal of attention. It is a complete depuration of even the foulest water, by causing it to pass through a filter composed of successive strata of sponge, sand, & charcoal—He succeeded with water taken from Dr. Wistar’s mascerating-tub, so putrid that the smell of it could scarcely be borne by the company. He has since extended his experiment, and, as he conceives with success, to the separating of fresh water from salt—not indeed by simple filtration, but by previously mixing with the salt water a certain substance, which he says is cheap and of small bulk comparatively. I fear however, that [he may] have been deceived, in these latter experiments—but as [he is?] preparing to repeat them with true sea water, the result, which I shall take the liberty of communicating as soon as known, will determine.

I have the honour to be with the most perfect respect & esteem Sir, your most obedient servant