Distance from Hensbarrow to Bodmin Down, 47337,2 Feet. Phil. Trans. 1797. p. 460.

No. of riangles

Observed
angles.

Names of stations.

Hensbarrow
Bodmin Down
Trevose Head

111. Trevose Head Bodmin Down Cadon Barrow

V.

Carraton Hill
Maker Heights
Black Down

Mean distance from Hensbarrow to Trevose Head, 78096,4 feet.

Diff.

42 33 52
71 55 27

O

77 20 18,5 -0,30

68 21 58,25-0,32

34 17 45,5 -0,23.

180 O 2,25

0,86 +1,391

Trevose Head from [Hensbarrow

Bodmin

-0,32
-0,43

Spheri-
cal
excess.

Cadon Barrow from {

30 58 13

-0,05 43 49 50,5 -0,04

Error.

74 5 22,5 -0,60

53 4 29 -0,48

52 50 9,75 -0,48

180

Angles corrected

for calculation. Distances.

"

H

O 1,25

1,571-0,32]

Maker

Black Down from {Carraton Hill

Bodmin Down

Brown Willy from {Cadon Barrow

43722 32488

Distance from Carraton Hill to Maker Heights, 82600,3 feet. Phil. Trans. 1797. p. 458.

Feet.

74 5 21,75

53 4 28,75
52 50 9.5

81967,6 78093

85625 60925

99680 82860,4

VII. Carraton Hill
St. Stephen's Down
Kit Hill

Observed
angles.

VIII. St. Stephen's Down

Black Down

Kit Hill

Diff.

0,89 -0,89

St. Stephen's Down from Carraton Hill

Black Down

70 15 32
37 1 56

{{

Distance from Carraton Hill to Kit Hill, 33427 feet. Phil. Trans. 1797. p. 459.

54 16 13

52 57 37

Spheri

cal excess.

-0,14 -0,11

Error.

<-0,19
<-0,19

St. Stephen's Down from{

Mean distance from St. Stephen's Down to Carraton Hill,

Angles corrected
for calculation.

Carraton Hill
Kit Hill

Distances.

Feet.

52991,3 62506,7

52994 52240,4

Black Down from St. Stephen's Down

f Kit Hill

Hence the mean distance from Black Down to St. Stephen's Down, is 62508 feet.

53128 62509,2

In the third triangle, the angle at Cadon Barrow is supplementary. When the observations were made at that station, a directionpost at Bodmin Down was mistaken for the staff, (to which it was similar in shape,) erected at no great distance from it. This error was not detected till long after: and, although it has been a maxim to which we have generally adhered, of observing all the angles of

1

each triangle, yet, for the reasons assigned in the preface, I have chosen to depart from it on the present occasion. In another principal triangle, the angle at Brown Willy is also supplementary : it has already been mentioned, that an instrument cannot be got on the top of it. As to the angles at Kit Hill, in the two last triangles, being inferred ones, it may be proper to mention, that Black Down was chosen for a station, after the observations were made the former. To have visited Kit Hill a second time would have been unnecessary, because there are not any distances, except to interior objects, which depend upon those triangles.

ART. XII.

Calculation of the Sides of a Set of principal Triangles, carried on from the Side which joins the Stations on Beacon Hill, near Amesbury, and Wingreen Hill, near Shaftsbury, towards the Base of Verification on King's Sedgemoor. Plate XXIX. Distance from Beacon Hill to Wingreen Hill, 114522,4 Feet. Phil. Trans. 1795. p. 501.

In the Philosophical Transactions for 1797, p. 455, the distance from Bull Barrow to Wingreen is said to be 69058, being 4 feet greater than the above conclusion.

Observed
angles.

ย

R

40 38 47,75 -0,28
45 43 3,5
93 38 12,5 -0,65

180 O 3,751

Diff. cal

-0,28

Ash Beacon from

Spheri

{

107 44 31
830

O

63 45 29

180

excess.

1,25 +2,50

Bradley Knoll
Bull Barrow

Angles corrected

for calculation. Distances.

23 4 15 -0,08 42 43 29,75 +0,07 114 12 18,5-0,97

180 0 3,25

1,17+2,08|

Westbury Down from{Bradley Knoll

Hill

40 48 1,75 -0,12 101 23 59 -0,48 37 47 58,5 -0,16

1179 59 59,25|

0,77 -1,52

Mendip Hills from{Bradley Knoll

Base of verification.-Greylock's Foss to Lugshorn Corner, 27680 feet.

/

"

40 38 45,25
45 43 3,25
93 38 11,5

23 4 14,75 42 43 28,25 114 12 17

40 48 1,75 101 23 59,75 37 47 58,5

107 44 31
8.30
6345 29

O

Dundon Beacon from Lugshorn Corner

Foss

Feet.

68650,6 75451

100625,1 58118,2

92954,0 61961,1

4561,5

29393

Xv111. Moor Lynch
Dundon Beacon
Mendip Hills

·

54 38 50

-0,07 101 22 54,5 -0,32

23 58 17

180 O 1,5

Moor Lynch from Greylock's Foss

Dundon Beacon

<-0,10

-1,0

Angles corrected
for calculation.

1+ 1,25

Moor Lynch from Lugshorn Corner
Greylock's Foss

105 40 0,5

59 58 14,5

14 21 45

-1,5

13 51 58,75 114 9 58,5 51 58 2,75

93 52 34,25
8

Dundon Beacon from Lugshorn Corner
Moor Lynch

78 7 15

o 10,75

Hence the mean distance from Moor Lynch to Dundon Beacon is 32688,85 feet.

54 38 49,5

101 22 53.75
23 58 16,75

0,5 +1,0

Moor Lynch

Mendip Hills from Dundon Beacon

Distances.

Feet.

8421,5 32688,7

32061,3 8421,8

4561,5 32689,0

78876,8 65622,7