368 
THE MEDITERRANEAN NATURALIST 
(10.) Thoroughly dry potatoes before storing j 
them, they will germinate’ and develop the ’disease 
in the pit or cellar. 
(11.) Store in a dry, cool place, and keep dry 
as warmth and moisture favour the growth of the 
fungi. 
(It.) Sort the potatoes in the cellar occasionally, 
and remove the infected ones, as the disease will 
spread from tuber to tuber. If a dry place is not 
obtainable, then dust the potatoes with dry, air- 
slaked lime, at the rate of one bushel of lime to 25 
bushels of potatoes. 
(14.) Plant on a sandy, loam, or a well-drained 
soil, as the moisture of a heavy or poorly-drained 
soil favours the disease. 
(15.) Plant in narrow patches running at right 
angles to the prevailing summer winds. This is 
based on the fact that the disease usually starts 
from a few infected plants, and the disease is spread 
by the wind. 
(16.) It has been recommended to soak the 
tubers for 24 hours in a solution of sulphate of 
copper; 6 ozs. dissolved in water is enough to cover 
a bushel. 
(17.) It has been shown that the fungus has 
been destroyed by keeping the tubers for a few 
hours at a temperature of 105 to 115 Fahr., a de- 
gree of heat that does not injure them for seed. 
This is a promising method, as it would thoroughly 
disinfect the seed, which is a source of the disease. 
(18.) Deep covering of seed and deep cove- 
ring in cultivation have been recommended. It is 
believed that deep planting is unfavourable to the 
fungus, and that the summer spores cannot reach 
covered tubers so quickly. 
(19.y Do not go through an uninfected field 
patch after walking throug an infected field; the 
.spores will be carried on the clothing, and spread 
the infection. 
(20.) Do not plant early and late varieties 
contiguous. 
The Effect of Pressure in causing a 
thinning of Soft Strata. 
It having been observed that, in many places in 
the Maltese Islands, the bed of clay that underlies 
the Coral Limestone has been much reduced in 
thickness, it has been suggested that the pressure 
of the overlying strata has had the effect of 
squeezing out the plastic clay beneath. The fol- 
lowing observations on the oxtent to which such a 
thinning out by pressure is mechanically possible 
may be of interest to students of Maltese geology. 
Suppose that AB (fig. 1) is a stratum of plastic 
clay, and that it is overlaid by the stratum of hard 
rock, CD. Let us suppose also that the strata 
terminate on the left with the escarpment AC, and 
that they continue indefinitely towards the right. 
The stratum of clay, AB, is supposed to lie on a 
bed of hard rock. 
Let us imagine the stratum of clay to be divided 
into a number of rectangular prisms of square 
section as shewn in fig. 1. If now the superincum- 
bent rock CD settles downwards, these squares will 
become elongated as shown in fig. 2, each prism 
being in-consequence shoved a little forwards by 
the pressure of the one behind, and the prism at 
the end will be sent beyond the face of the 
escarpment. 
