34 ALTERED SILICEOUS SINTER FROM BUILTH. [ Feb. 1902, 
these he alludes in his ‘ Outline of the Geological History of the 
Rocks around Edinburgh,’ read in August 1897, and published in 
Proc. Geol. Assoc. vol. xv, where at p. 129 he states that 
‘Concurrently with the upgrowth of the volcano there arose hot springs, and 
perhaps also geysers. From these were deposited beds of calcareous and 
siliceous sinter, which were spread out in thin layers in the vicinity of their 
orifices.’ 
Although neither have I had an opportunity of examining this 
siliceous sinter, nor can I find any reference to its microscopic cha- 
racters in the paper just cited, it is only right that I should give 
due credit to its discoverer, whose careful work has always com- 
manded my respect. — December 4th, 1901. | 
EXPLANATION OF PLATE II. 
Fig. 1. Siliceous sinter (pumice-bearing). Builth, Brecknockshire. x 140. 
Ordinary transmitted light. 
2. The same part of the section. x 140. Crossed nicols. 
3. Siliceous sinter (pumice-bearing and with a few fragments of felspar). 
Rotorua, New Zealand (H;,). x 140. Ordinary transmitted light. 
4, The same part of the section. x 140. Crossed nicols. 
5, Siliceous sinter, showing brown matter probably of organic origin. 
Builth, Brecknockshire. x 140. Ordinary transmitted light. 
6. Siliceous sinter (pumice-bearing), showing brown matter, probably of 
organic origin. Rotorua, New Zealand. x 140. Ordinary trans- 
mitted light. 
7. Fragment of pumice in siliceous sinter. Builth, Brecknockshire. 
x 140. Ordinary transmitted light. 
8. The same. x 140. Crossed nicols. 
