In my last Letter I gave you some account of the extent of the Commerce and of this Country, and as I am convinced that common Report of estimation of Distance, &c., will not be satisfactory to a Philosophic mind, and as I have had an opportunity of seeing a map or chart of that Country made by a Gentleman of observation and Science, who has actually traversed it and made his map in it, and with whom I have this week had several Conversations, with the map before me, I am able to give you all the satisfaction you wish for, exclusive of the map itself, which I could not get a copy of, but I hope to send it to you the next Summer." (The "Gentleman" here referred to was none other than Peter Pond, of whom mention has already been made at some length.)

"From out of Great Slave Lake runs a very large River, which runs almost South-West, and has the largest Falls on it in the known World; it is at least •two miles wide where the Falls are, and an amazing Body of Water. This River leaves the Lake in Lat. 64° and Long. 135°, and the Falls are in Long. 141°.

"The great chain of Mountains that extend from Mexico along the Easternº or Pacific Ocean, and the Northern Pacific Ocean, terminates in Lat. 62½° and Longitude 136°, so that the Slave River runs to the Westward of them, and emptys into the Ocean by its course in about Lat. 59°.

"There is no wood to the Northward of Slave Lake, and there is only a little low Brush which is filled with a species  p300 of Buffaloes which have no Tails, but have long Hair on the Back of their Thighs and Legs that resemble a Tail. They are smaller than the common Buffaloes.

"When you have proceeded thus far, and have looked over your map, you will readily conjecture what River the above Slave Lake River is known by, when it empties into the Ocean. To save you much Trouble I will tell you it is Cook's River, which he penetrated upwards of 70 Leagues North-Eastwd., as you will see by his chart. Cook's River, as he laid it down in his chart (that is the Mouth of it), lays in Lat. 59°‑40′ and Long. West 154°.

"His calculation and laying it down was East Longitude, but if you deduct his Eastern Long. from 360 you will find it to be 154 West. His course up the River was North-Easterly, the course of the River out of Slave Lake was South‑Westerly.

"He traversed his River that course near 70 leagues North‑Easterly, the River out of Slave Lake is known as far South‑Westerly, therefore the distance to form the Junction or to ascertain the River to be the same is very short. The Mouth of Slave River at the Lake is in Lat. 64° and Long. 134°. The mouth of Cook's River is in Lat. 59°‑40′ and Long. 154°. The Course is North‑Easterly and South‑Westerly. The Degrees of Long. in that Lat. are but little more than •26 miles upon the Average to a Degree, and the Difference of the Lat. only about 4 Degrees. Hence, as there is no other known Vent for the River setting out of Slave Lake, nor any other River in that Country to the Northward or Southward of Slave Lake to form such a River as Cook's River, there can be no doubt but the Source of Cook's River is now fully discovered and known. There are other proofs that are incontestable — Cook found a great quantity of drift‑wood on the Coast. This wood is only found on the Banks of the River that empties into Slave Lake. Neither are there any Rivers of any size from the near Approach of the Mountains to the Sea to the Eastward of the Lake. The Rivers of Arabaska (Athabasca — Ed.), Slave, and Mountain which empty into Slave Lake, are annually twice overflown — in the month of May by the breaking‑up of the Ice, and in the month of August by the Melting of Snow on the Mountains. Hence, then, is accounted for the quantity of drift‑wood which Capt. Cook met with, and these could only be launched into the  p301 Ocean from Cook's River — for as I have already observed, there can be no extensive River to the Southward of Cook's River, or the River that empties out of Slave Lake, as the great Chain of Mountains approach to the verge of Slave Lake and River.

"Another Proof is that the Gentleman (from whose Chart and from whom I collected the above Information) met with two Indians, who came, as they said, up a River from the Northern Pacific Ocean all the way to Slave Lake.

"They brought him in 1787 a Blanket which they received from Vessels which were at the Mouth of the River; they say that the River he was in is large to the place of Discharge and Navigable, so that if we take the Latitude and Longitude of the two Rivers, the Courses, and all the other circumstances into consideration, little doubt remains that they are the same. . . .

"The Inferences that I shall now draw are . . . That the Great Slave Lake is the most Northerly large piece of water before you arrive at the Northern Ocean, and the River that rises from the Lake empties into the Northern Pacific Ocean, and is the River that Cook discovered. That an easy communication with and an advantageous commerce may be carried on by posts established on Lakes Slave, Arabaska,º Pelican, &c., &c., and to deliver the Fruits of their Commerce at the Mouth of Cook's River, to be then carried to China, &c., and that as Cook's River and the Lands on Slave Lake, Arabaska, &c., are very fine, some advantageous settlements may be made there which may be beneficial to the Government.

"The Country about Arabaska is exceedingly fine, and the Climate more moderate than it is here, which is owing to its Propinquity to the Western Ocean. The distance is not more than 200 Leagues, if so much, on a West South-Western Course. We have a Post there, as we have on the different Lakes from Lake Superior to the upper end of Slave Lake; the number of Posts is 21 in that distance where Traders are posted to trade with the different Tribes of Indians.

"The distance from this Town to the Head of Lake Superior is 750 Leagues, and from the Head of Lake Superior to the Great Slave Lake is one thousand Leagues; in the whole, 1750 Leagues.

"The person from whom I had my Information is Peter Pond, who was supplied with the proper Instruments here to  p302 take his Latitude, and instructed fully in the knowledge of Astronomy, &c., &c. His Latitude is undoubtedly Right, and his Longitude is near Right. It was taken by some Persons sent from York River •seven hundred miles to the westward of it, and from thence by the Courses of the Rivers and Lakes, no great mistake can be made.

"Another man by the name of M'Kenzie was left by Pond at Slave Lake with orders to go down the River, and from thence to Unalaska, and so to Kamskatsha,º and thence to England through Russia, &c. If he meets with no accident, you may have him with you next year."

"Sir, — Having received from my son, Isaac Ogden of Quebec, a letter, dated 7th Novem. 1789, giving an account of a Mr Pond's having explored the interior parts of North America, I have the honour to inclose you an extract of said Letter, as the same may afford some advantageous Information to Government, which, if you think proper, you will lay before Mr Grenville.​1

I have the Honour to be, Sir,

Your most obedt. and very humble serv.,

David Ogden.

" Rathbone Place, No. 50,
January 23d, '90."