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Secondary , or Tertiary . — Allusion was made to the Tertiary 
basalts of Mull, and to the possibility of there being other igneous 
rocks of that age on the mainland. A section of Arthur’s Seat was 
exhibited, showing a series of volcanic eruptions, resting quite un- 
conformably upon some of Carboniferous date. This later group 
must be greatly posterior to that below; and the author collected 
evidence to show that it may be regarded as later Secondary, or 
older Tertiary. 
Letter from the Rev. Dr Livingstone, F.R.S., to Dr Lyon 
Playfair, C.B. 
River Shire, 28 th Oct. 1859. 
My dear Dr Playfair, — -We left England in April 1858, and up 
to this time we have not received a single private letter from home. 
This saves me the trouble of apologising to any of my friends whom 
I have neglected. So here goes into the middle of things. We 
have just traced this river up to its point of emergence from the 
hitherto undiscovered Lake of Nyassa or Nyinyessi. This discovery 
is of more importance than at first sight appears, for it opens a 
cotton-field superior, I imagine, to the American, inasmuch as 
there are no frosts to endanger or cut off the crops ; and instead of 
the unmerciful toil required to raise the staple there, one sowing of 
foreign, probably American seed, introduced into several parts by 
the natives themselves, serves for three years’ crops. Even when 
burned down, the plants spring up fresh again. It may have dis- 
advantages to counterbalance these points in its favour, but of these 
I am at present ignorant. There is a good day’s channel from the 
sea at Kongone harbour up to Murchison’s Cataracts in lat. 15° 
55' south. We have then only 33 miles of cataracts, past which a 
common road could easily be made — and the Shire itself is again 
navigable right into Nyassa in lat. 14° 55' south. Above the 
cataracts the land is arranged into terraces east of the river. The 
lower or Shire Valley is about 1200 feet high, and exactly like the 
valley of the Nile at Cairo, only a little broader. The second 
terrace is over 2000 feet and three or four miles broad ; the third over 
3000, or about equal to Table Mountain at the Cape (long spoken of 
as the highest in South Africa). We travelled in the hottest season 
of the year, or that called in the West the “ smokes,” when, from 
