Calcite from Luganure. 337 
render the faces oR subordinate to them, it would pass into the 
form No. 2 from Weardale. I have, indeed, found a few imper- 
fect crystals from Luganure, in which the prismatic faces are only 
rudimentary, the outline of the tabular crystal being rhombo- 
hedral. 
Although, as I have above observed, the prismatic faces oR 
are sometimes dull, the combination of brilliant nacreous oR 
faces with wax-like prismatic faces exactly like those character- 
istic of the faces ooP is, so far as I am aware, extremely rare. 
In the mineralogical collection of the Museum of Irish Industry 
there is a specimen from Andreasberg, in tabular crystals some- 
what thicker than those from Luganure, which I have described. 
The same kind of rudimentary facets occur in the alternate 
basal edges. I have not had an opportunity of determining 
whether they belong to 3R/ (b!). The prismatic faces have the 
wax-like dullness of the Luganure specimens ; but the crystals 
are opake, and the faces oR are dull, and in other respects 
very different in appearance from those just mentioned. In the 
same collection, characteristic specimens of the other forms from 
Luganure which I have mentioned are to be found, as well as 
of several others, of which I have not yet been able to procure 
specimens *, 
* It is to be regretted that the descriptions, both crystallographic and 
mineralogical, of the minerals from Irish localities, which are to be found 
in Irish collections, have not been more generally published. It is only by 
the careful study of the conditions under which certain forms of minerals 
are found, the first element of which is a faithful record of the circumscribed 
localities in which they occur, that we can hope to arrive at a solution of 
the important problem in molecular physics—the causes which produce 
modifications of form in bodies. The‘ Manual of the Mineralogy of Great 
Britain and Ireland,’ by Robert Philips Greg, F.G.S., and William G. 
Lettsom, forming one of the admirable series of Manuals published by 
Van Voorst, is a most praiseworthy step in this direction. It is with regret, 
however, that I have to state that this otherwise excellent and useful work 
is full of errors regarding Irish localities, —errors, too, of the strangest kind, 
not mineralogical, but geographical, and which one would scarcely expect 
to find made respecting the divisions of an Asiatic country. I do not speak 
of such errors as Rovenagh and Borenagh for Bovevagh (pp. 54 and 88), 
Bum Beg for Bun Beg (p. 101), or Glen Maceness for Glenmacnass, which 
are, however, too numerous to be pardonable, but of such errors as County 
of Cavenagh for County of Cavan (p. 20); “ Ballygahan mine, at Glandore, 
County of Wicklow” (p. 279), Glandore being in the County of Cork; 
“Knockmahon and Tigroney in Waterford” (p. 305), Tigroney being in 
Wicklow; “In Wicklow, at Audley mine” (p. 311), Audley mine being 
in the County of Cork. I hope a second edition will enable the authors, 
not only to correct these errors, but to greatly extend the list of localities. 
