+---------+----------+---------------+----------+------------+-------+ | 1802. | Lat. | Long. | Course. | Var. | Diff. | +---------+----------+---------------+----------+------------+-------+ | April | | | | | | |22. A.M. | 39° 38´S.| 141° 40´E. az.| W.S.W. | 11° 52´E. }| | |24. | 39 38 | 144 1 | S. | 7 59 }| 3° 53´| | July | | | | | | |15. P.M. | 34 5 | 135 9 | S.E._b_E.| 1 33 W. }| | |-- | 34 6 | 135 9 ampl. | S.W._b_W.| 3 56 E. }| 5 39 | |28. | 25 0 | 153 23 | N.W._b_N.| 9 39 }| | |29. | 24 43 | 153 27 | S.E.½S. | 6 33 }| 3 6 | +---------+----------+---------------+----------+------------+-------+ After such a coincidence, the fact of the variations depending greatly on the ship’s course cannot possibly be called in question; though it is certainly surprising that it has not been sooner attended to in the way that it deserves, by other navigators; for it did not altogether escape their observations. Mr. Wales, astronomer to Captain Cook’s ship, the Resolution, had made the same observations in a pretty accurate manner; and M. Entrecasteaux, though without assigning any cause, says, that the “Compass showed differences of several degrees in variation at sea, though observed with the greatest care, and within the space of a few minutes.” After a more enlarged series of observations shall have been taken, and after the attention of astronomers is directed to this fact, we may confidently expect a most important improvement in the science of navigation. No. V. The following article, “ON THE TREMENDOUS CONCUSSIONS OF THE FIELDS OF ICE,” in the Arctic Sea, is extracted from Mr. Scoresby’s valuable Memoir on “Polar Ice” in the Wernerian Society’s Transactions. “The occasional rapid motion of fields, with the strange effects produced on any opposing substance, exhibited by such bodies, is one of the most striking objects this country presents, and is certainly the most terrific. They not unfrequently acquire a rotatory movement, whereby their circumference attains a velocity of several miles per hour. A field, thus in motion, coming in contact with another at rest, or more especially with a contrary direction of movement, produces a dreadful shock. A body of more than ten thousand millions of tons in weight,[38] meeting with resistance, when in motion, the consequences may possibly be conceived! [38] A field of thirty nautical miles square surface, and thirteen feet in thickness, would weigh somewhat more than is here mentioned. Allowing it to displace the water in which it floats, to the depth of eleven feet, the weight would appear to be 10,182,857,142, nearly in the proportion of a cubic foot of sea water to 64 lbs.