MATHEMATICAL PAPERS. 147 
anachromatic, made by Do/land, it's magnifying power go. The 
Reverend Profeflor Wigglefworth and Mr. Sohn Mellen, ufed 
two of the telefeopes. Mr. Mellen obferved with the achro- 
matic. 
The obfervers were fo unfortunate as not to perceive the be- 
ginning of the eclipfe. They fuppofed the fhadow would have 
entered the fun’s difc more wefterly than it did.— They there- 
fore attended to a different part of the fun's limb. To prevent 
a fimilar error in future, it might be weil, previoufly, to deter- 
mine the point at which an eclipfe will commence. This may 
be done by calculating the angle, which the ecliptic will make 
with a vertical circle pafüng through the centre of the fun, at 
the time the eclipfe begins. 
The obfervations were as follow, viz. 
Obfervers, Wiggle/worth. Gannett. Mellen. Mean of obf. 
Apparent Time.. 
Put Conta OF IN. We 10s, [x ^ WO "^" Bot ^ Mtv 
Plate IL Fig. VI. Tr 26: Yi 1653941 ^41 39 O0 
"Total obfcuration of ditto, 11 25 Xf 13:25 36 15 25 tei 
Fir cont..of NE. fpots, No. 1, 131 31 36 11 31 53 11 31 38) «1b 31 42k 
, 2, 11 33 4 1133 4 
$ Ii 33 54 11 33 54 
Total obfcuration of &. 11 54-52 P134 58 1434 55 
Firft cont. of central fpot, 11 36:900 13 $5 $0. 25 35 LI 35 28 
tal obícuration of ditto, — 11 3619 11 36 4 11 36 14 Ib 36 125 
Firft cont. of S. E "Kd 19 427 42:49 47 39 13 47 
curation of ditto, — 14 1 13914 4. iri4 3$ 
Total emerfion of N. W. fpots, 12 29 28 I2 29 28 
Firftapp.of N.E.fpots, No.1, 12 52 56 12 52 33 12 52 31 12.52 36$ 
2, 12 $3 27 12. 53 27 
3x 12 54 9 12 $4 9 
4 12 55 23 12 $6. 4 12 55 43} 
Fir app. of central fpot, 12 $6 ít 12 56 11 
Total emerfion of ditto, ia $6.47 12 3645 12 56 46 
Firft app. of S. E. fpot, Pay tt P1364 — 1 13149 
Total emerfion of ditto, Iu 1 &- s 1 34 3 
End of the eclipfe, 1 39 531 13947  Á 139590 1 39 49% 
The obfervers not being poffefied of a micrometer, Mr. 
Wigglefworth made whe of the following expedient to determine 
12 
the 
