5 2 NATURAL HISTORY 
difadvantages : our coaft is not only extended greatly in proportion 
to the area of land, but it has many promontories jutting out on 
each flde, which neceffarily make deep bays, and unhappily aug- 
ment the diftreflfes of failors in ftormy weather : another inconve- 
nience of our Sea-fituation is, that the land fhooting out fharp like 
a wedge into the Atlantic Ocean, fhips oftentimes miftake one 
channel for another, or are drawn alide from their true courfe by 
the inequality of the tides. Farther : The irregularity of the tides 
riling from the prominency of the head-lands, is alfo increafed, at 
the extremity of Cornwall, by the Scilly Illes, which narrow the 
channel (whether the tide fets to the North, or the South) ; and con- 
fequently, increaling the velocity of the current, promote a more 
than ordinary indraught into both channels. The tide of flood at 
the Land s End riles on the top of a common Ipring eighteen feet, 
and from that to twenty-four, according to wind and weather ; 
infomuch, that in ftormy weather, from the South-Weft, it has 
rifen to the height of thirty feet ; but at the common neap tides 
only thirteen feet ufually, and at a very dead neap it has not rifen 
above ten feet. During the flood, the tide at the Land’s End 
fets inward from the South near nine hours ; its run is eight 
hours in moft places betwixt Scilly and the Land’s End ; but the 
ebb continues only betwixt three and four hours. This is a very 
dangerous Angularity, if not known, and properly regarded ; but 
the greateft difficulty of all, which our maritime Atuation lies under, 
is this ; that an accurate furvey of our fhores, and a precife deter- 
mination of our latitude and longitude, has never yet been taken, 
not fo much as of the Lizherd, the flrft land ufually made by Ihips 
homeward bound, and the Southernmoft point of England, from 
which moft fhips outward-bound to the Southward begin their 
reckoning : here a falfe ftep is made at flrft fetting out, and unlefs 
rectified by repeated obfervations, it may be of fatal confequence. 
To have the longitude and latitude afcertained at the extremity of 
the ifland where fhips begin and end their reckonings, is certainly a 
matter of the greateft moment to commerce, and ffiould be per- 
formed by a variety of the beft inftruments, at lublequent times, and by 
more than one Ikillul hand. This has never yet been done, (fee 
before, chap, i.) nor will be probably, but by the interpofltion of 
the government, whofe attention and nomination of proper perfons, 
and proviflon of a fufficient apparatus of aftronomical inftruments, 
(an expence feldom within the reach of a private purfe) this matter, 
I Ipeak it with fubmiffion, feems to me exceedingly to delerve. 
Another circumftance claims the attention of our countrymen ; 
our harbours are generally at the mouths of rivers, and not very 
diftant from the hills where they rife, and of courfe not fo long or 
deep 
