178 Miscellanies. 
in the transit of a single wire is seldom over .3 of a second; and the 
mean of the 5 wires of the instrument would, therefore, render the proba- 
ble error certainly Jess than .1 of a second. The error arising from it- 
regularity of the clock’s rate is rendered of comparatively little mbment 
by the fortunate coincidence, nearly, of the transit of Antares with the 
middle of the eclipse. -The only remaining error of importance, that of 
the imperfection of vision, in noticing the first moment of ingress, may 
be presumed to be very small, from the.circumstance that the observa- 
tions were entirely independent, at two different clocks, in separate 
apartments, and the coincidence of results was not mutually known till 
some minutes afterwards, thereby preventing the otherwise natural result 
of catching the first glimpse by contagion. “The agreement of the times 
of commencement to less than .2 of a second, under such circumstances, 
goes far to prove their accuracy. The clocks were compared by coinci- 
dent beats immediately before and after the ingress. 
The distances of the cusps are uncorrected for difference of refraction, 
which, in the last measures, is of considerable amount. If any of them 
should be found discordant with the others, from error in counting from 
the clock, or in registering, they will easily be discovered in the calcula- 
tion, and corrected, if the mistake is evident, or otherwise entirely re- 
jected. 
3. Supposed new mineral at Bolton, Mass —The following angles were 
obtained with the reflective goniometer, from a small er fa gr 
inert sparingly disseminated in massive Scapolite, at the Bolton lime 
at occurs in small isolated prismatic individuals, imperfectly 
, or in divergent groups of slender flattened prisms, more or 
less perfect. The mineral has been considered Gadolinite, and by Prof 
Surrarp, who early observed it at the above locality, as Allanite, to which 
it is closely allied, if not identical with it. 
The primary is an oblique rhomboidal prism, M : T = 113° a5 and 
66° 15’, M: é (replacement of obtuse lateral edge) = 149°, T : é = 144° 
45',M:€ (vepliiocanent of acute }ateral edge) = 128° 45’, T : é== 117° 
30’, €: € = 97° 45’ and 82° 15’. The crystals are flattened parallel 
with €, and slightly sieaaihla some varieties of green hornblende. M is 
bright, T much less so ; € is deeply channeled. No cleavage a 
H. = 575. G. as fund by Prof. S. 3—3.25, the former obtained wit 
fragment weighing 1.2 grains ; the latter, with 2 céntigrammes, OF a 
one third of a grain. Lustre, resinous; streak, greyish or greenish white. 
Color, grass green—blackish green ; raindacts t—subtranslucent ; brittle. 
A black variety occurs in the Petalite of the samme quarry, which, in 
lutre and and colar, much resembles Allanite. The above angles and other 
ts seem, however, to indicate that this mineral is a distinct 
apc If it should prove, ~_—— on further ee. identical 
Ss Sa 
i 
bas 
