106 TlMEHRl. 
Further search would, no doubt, bring to light local 
tannin material of a richer and better quality than any 
yet examined ; but even those at present known should be 
sufficient to form an important industry for the colony." 
Again, although the mineral productions of Guiana are 
neither numerous nor important, another example of 
our neglect of useful products was represented at the 
Exhibition by a sample of a mineral earth, shown by 
Mr. JOHN Sealy, which is described in the following 
letter : — 
Dear Sirs, — We have carefully examined the mineral powder sent 
us by you, and have consulted several of our friends as to its commer- 
cial value. The mineral is in the main hydrated protoxide of iron, 
aluminia, with small proportion of lime, magnesia, sandy grit or 
silicious matters, and magnetic iron. It contains the merest trace of 
gold, and no silver. On being heated to a dull red heat, it loses part 
of its water and assumes a darker colour. The heating of part of the 
sample sent us must have been very imperfect ; as there is hardly any 
perceptible change of colour. It does not harden in water ; is therefore 
not a pozzolona. It is however a very useful, and we might say 
valuable pigment quite equal to terra di Sienna from which it can 
hardly be distinguished. The colour, when rubbed in oil, is deep and 
pleasing, and the value of the article, for large quantities is estimated 
at from £2 to £3 per ton. 
Your's, etc., 
LUTCHNING k CO 
But it is now time to review briefly and in order the 
various contents of the Exhibition. 
As regards the sugar shown there is little to be said. 
There were the usual beautiful white crystals, of little 
commercial value ; there were the usual straw sugars ; 
and there were for the first time, or at least the first 
time in any number, samples of the dark coloured re- 
