ARTIFICIAL STONE MANUFACTURE. 963 
the left the plane of polarization. Important data like these, 
furnished by optical analysis powerfully contribute to the elucidation of 
certain questions connected with the presence and the formation of the 
different kinds of sugar already enumerated in the vegetable organiza- 
tion, optical saccharimetry employed in conjunction with the ordinary 
methods of chemistry, has already produced invaluable results. 
(To be continued.) 
ARTIFICIAL STONE MANUFACTURE. 
That artificial stone of a durable quality can be made in most places 
and in any quantity is a proposition that may readily be granted ; but 
when the further question for agricultural purposes at a sufficiently low 
price is appended, its successful reduction to practice becomes somewhat 
problematical. At the same time it must be admitted that this branch 
of art has of late been making considerable progress ; that some impor- 
tant discoveries, which have hitherto been imperfectly carried out under 
patent and a too limited means, are becoming the common property of 
the public ; and that the advances being made in the sister-branches of 
chemistry and mechanics are fast bringing it within the range of profit- 
able practice, if we have not already attained this position. 
The subject suggested itself to our notice the other day, in witnessing 
a labourer taking up an old gate-post, which had been fixed and held 
firm in its place by well-tempered concrete, the subsoil being a soft 
tenacious example of London clay. The concrete was as hard and solid 
as if it had been run together in a state of fusion like lava, or some 
specimens of conglomerate rock, making the pick ring at every stroke 
in breaking it up. To appearance, from a passing observation, it had 
preserved the gate-post from rotting below the surface, and held it aa 
firm in its vertical position above ground as if it had been an iron post 
fixed in solid rock by lead. No doubt both these conditions depended 
in a great measure upon the soundness of the post when put in, together 
with the quality of the wood and concrete. This may be granted ; but 
it is only profiting by the lesson which examples of more than ordi- 
nary success teaches, that leads to permanent improvement ; for 
although some may fail in setting gate-posts firm in concrete, that 
is no rule to the contrary, but only proof practical of mismanagement. 
Fixing gate-posts, however, is not the only agricultural purpose in 
which concrete can be used, as many of the old Pictish concrete build- 
ings still standing prove. Some of these old castles thus referred to 
lead us back to periods lost in ages gone by, and to appearance seem as 
if they would stand to the end of time, the influence of the weather 
upon their structure not being greater than upon the solid rock that 
