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 less than .1 of a second. The error arising from ir- 

 regularity of the clock's rate is rendered of comparatively little moment 

 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 crystal of a green 

 mineral, sparingly disseminated in massive Scapolite, at the Bolton lime 

 quarry. It occurs in small isolated prismatic individuals, imperfectly 

 crystalline, or in divergent groups of slender flattened prisms, more or 

 Jess perfect. The mineral has been considered Gadolinite, and by Prof. 

 Shepard, 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° 45' and 

 66° 15', M : e (replacement oUbtuse lateral edge) = 149°, T : e = 144° 

 45', M : e (replacement of acute lateral edge) = 128° 45', T : e = 117° 

 30', e: e= 97° 45' and 82° 15'. The crystals are flattened parallel 

 with e, and slightly resemble some varieties of green hornblende. M is 

 bright, T much less so ; e is deeply channeled. No cleavage apparent. 

 H. = 5.75. G. as found by Prof S. 3 — 3.25, the former obtained with a 

 fragment weighing 1.2 grains ; the latter, with 2 centigrammes, or about 

 one third of a grain. Lustre, resinous ; streak, greyish or greenish white. 

 Color, grass green — blackish green ; translucent — subtranslucent ; brittle. 



A black variety occurs in the Petalite of the same quarry, which, in 

 lustre and color, much resembles Allanite. The above angles and other 

 characters seem, however, to indicate that this mineral is a distinct 

 species. If it should prove, however, on further examination, identical 



