will meet with encouragement in a community where they are so strongly required. I have for this purpose endeavoured, not always indeed with perfect success, so to form my collection as to show, not only the ganguethe kind of stratum in which minerals are imbedded-but, as much as possible, the minerals found in the immediate vicinity. Had my present ideas occurred to me at first, I should have succeeded more completely by con. stantly keeping this object in view. But having to search out my own path, without the aid of an instructor, and, for some years, far from all the usual sources of information, my notions on the subject were, for a long time, vague and crude. Feeling my own want of elementary knowledge at the outset of my inquiries, I have presumed to occupy the present situation, in hopes of being able to guard others against much waste of precious time, and many errors that so long obstructed my own course of investigation: and without pretending to profound knowledge of the subject, I hope I shall be able to give a little of that assistance to others, which I should have been so glad to have received at the cominencement of my own career.

The following advertisement is taken from the daily gazettes, and will give our readers a general view of the topics which are to be discussed by the learned professor. ED.

The undersigned proposes to give a course of mineralogy at the university in Ninth-street, to commence the middle of November; the lectures to continue three times a week, until the course is completed, which is expected to occupy ten or twelve weeks. The following is an outline of the plan proposed to be pursued:

1. Introductory.

2. On the Globe of the Earth. On the general characters of Minerals, specific gravity, hardness, fracture, chrystallization, phosphorescence, &c.

3. On the Rocks termed PRIMITIVE, and their component parts. 4. On the substance found in primitive rocks so called.

5. On the Rocks termed TRANSITION, and their component parts. 6. On the substances found in the Transition Rocks, so called.

7. On the Rocks termed SECONDARY, and their component parts,

8. On the substances found in Secondary Rocks, so called.

9. On VOLCANIC formations, or Lavas.

10. On the Substances found in Lavas.

11. On ALLUVIAL Deposits.

12. On BASINS: On the great Mississippi Basin: on the Basin at Richmond, Virginia: on the Paris Basin: on the London Basin: on the Isle of Wight Basin.

13. On Organic Remains.

14. On Geological Theories.

The course will be illustrated by a very extensive Mineralogical collection.

THOMAS COOPER, M. De

FOR THE PORT FOLIO.

LETTER FROM THE REV. MR. MINES TO MR. H. HALL, ON JONES'S

WHEAT,

Leesburg, 1st July, 1817.

DEAR SIR,

Having seen some inquiries, respecting the Jones's (here more commonly called Lawler) wneat, by the Agricultural Society of Philadelphia; and also your letter addressed to their Secretary, I take the liberty to communicate to you some observations which I have made on this subject.

I believe the Jones' wheat will effectually resist the Hessian fly. My wheat was sown about the 10th of October, and grew well; having, I thought, a little of the purple appearance of rye. When it began to spread and shoot up, about the middle of April, it gradually assumed more and more of what the farmers term the fired appearance. This was occasioned by the two under or ground blades turning yellow and gradually decaying. The plants, however, grew and shot up with vigour. The two under blades still continued to decline, until they became entirely dead, in the early part of May. So that this particular property of the wheat, which at first alarmed me, not being accustomed to the manner of its growth, I believe saves it from the injury of the fly. Upon examination, at the season when they are committing their depredations, the fly will almost universally be found, in its imperfect state, in the two ground blades. Now if these die before the eggs arrive at any considerable size, they have neither protection nor nourishment, and must of necessity perish.

From these facts I conclude that the Jones' wheat or any other species, of which the under blades die carly, will be proof against the ravages of the Hessian fly. Facts in this part of Virginia confirm this conclusion; for in no instance, that I have seen

or heard of, has the Jones' wheat been injured by the fly, and every other kind, even sown adjacent and on the same day, has sustained much damage.

I shall proceed now to some general observations respecting that diminutive yet mighty destroyer, the Hessian fly. And though I farm but 19 acres adjacent to this village, as much for health and rerecreation as for profit; yet I rejoice that the disasters of the present season have produced a general effort against this formidable enemy. From every observation I have made, I have come to the same conclusion, that the fly deposits its nit or egg in the grain of wheat, in its soft or ripening stage. This opinion arises from the following facts.

1. Wheat sown early in autumn is frequently destroyed by the fly. The reason appears to me plainly this; there remains a sufficiency of warm weather together with the forward state of the plants to mature the fly, so far as to destroy or greatly injure the vegetation. Hence the crop is often lost by too early sowing.

2. Wheat sown late in autumn, say the latter end of October or beginning of November, is more generally destroyed in the spring than any other. The reason is, that the nits or eggs are not enlarged in autumn, either by the luxuriance of the plant or by warm weather; and consequently all pass the winter unhurt; and matured by the vernal suns and vegetation of the plants, as an army unbroken, are prepared for the work of devastation.

3. Wheat sown from the first to the tenth of October, is found to escape the ravages of the fly better than that sown at any other time. The reason is clear, in perfect accordance with the above theory. A portion of warm weather remains, after the sowing, sufficient to swell a part of the eggs in some degree, though not so much as to injure the wheat, yet so much as to ensure their destruction by the winter frosts. Hence a part of the eggs are destroyed, and the remainder being less forward in autumn remains till spring.

4. The flies are matured through the month of May and the first part of June; hence they are ready to deposit their eggs when the grain is forming. But flies are sometimes, though very rarely, found in the higher joints of the stalks. These I apprehend are deposited on the top of the stalk before earing, or in the joint by those that have obtained a premature growth, or have come to perfection before the usual season.

The theory of the deposite in the grain, appears to me not only plausible, but supported by all the facts of the case. And the fact of the eggs being found in the two under blades confirms it, I think, beyond a doubt, for these spring immediately from the grain, and embrace the egg in their formation. Now if the deposite be in the grain, could not some means of extermination be found? Perhaps quick lime with the wheat, when soaked for sowing, would have the effect as has been suggested by some. I think, however, that the soaking ought to be of longer duration, or in milk warm water, so as to bring forward and quicken, if possible, the nit deposited in the grain, previous to the application of lime or any other substance intended to destroy it. I am persuaded that useful experiments might be made, by applying to the eggs found in the wheat, in May, different substances or solutions, without detaching them from the stalk. It might be discovered what substance or solution, lime, or lime water, or any other, would most effectually corrode and destroy them, and in the least time. The same substance or solution, applied to the grain well soaked, would doubtless have a similar effect. The present season is too far advanced, perhaps, to obtain the fly in the proper state for such experiments, as they should be made when the nit is small; yet, I think it well worthy of attention hereafter.

I am, &c.

JOHN MINES.

GODFREY'S QUADRANT.

TO THE EDITOR OF THE PORT FOLIO.

SIR-I send you an extract from a letter which was found among the papers of the late Dr. John Ewing, in his hand-writing. It affords some testimony on a question in which our national feelings are interested; and it comes from an eminent philosopher who lived at the time, and was peculiarly well qualified to form a just opinion. Dr. Ewing had read some observations on the double sextant, in the American Philosophical Society, which produced "Remarks" from a Mr. Ludlam (in the Gentlemen's Magazine for Aug. 1771.) This letter is in reply to these "Remarks;" but I shall only copy what answers my present purpose. J. E. H.

"But what seems to have destroyed Mr. Ludlam's temper and betrayed him into a warmth of expression which I did not expect from a gentleman of candour, is my unluckily calling the instrument by the name of Godfrey, and saying that he first invented this useful instrument. He alleges that my intelligence was but private and of doubtful authority;—that we "have not even oral tradition concerning the perfection or imperfection of Mr. Godfrey's invention," that "it is not related, how far it answered the purposes of navigation;" that " one would suppose, it did not answer at all," and that it is " a ridiculous vanity now to call it by his name."

"To convince Mr. Ludlam that he is mistaken in all these rash and ill-grounded assertions, and to do justice to Mr. Godfrey's character, is my principal motive in making these observations; as I look upon all he has said concerning the instrument, as the effect of a querulous and hypocritical taste, and indeed only designed to pave the way for his feeble attempt to secure the honour of the original invention to Mr. Hadley. He is candid enough to mention a letter of Mr. Logan, in which he says that "a reflecting instrument made by Mr. Thomas Godfrey was taken to sea, and brought back again before the end of February, 1730-1." But in order to make Mr. Hadley's instrument prior to Mr. Godfrey's, he supposes that Mr. Hadley had spent 4 or 5 months in constructing and perfecting so new and uncommon an instrument as he had produced" in the month of May following. But might not Mr. Godfrey spend as much time in contriving and preparing his instrument for trial at sea? To which add three months for the voyage, and then Mr. Godfrey's invention must have been at least half a year before Mr. Hadley's. But there is no need of having recourse to groundless supposition in this matter. In the American Magazine for the months of Aug. and Sept: 1758, printed in Philadelphia, by a society of gentlemen, I find three letters, one from Mr. Godfrey to the Royal Society, and two from Mr. Logan to Dr. Hadley and the Royal Society, concerning this invention. In one of these Mr. Logan gives Dr. Hadley a full description of the reflecting instrument Mr. Godfrey constructed; which appears to be the very instrument now in common use; some very trifling differences in the construction only excepted, which might have been made by Mr. Hadley, and which are hardly worth