MMHI 
ELI 
are productive of distempers in trees, of 
which they are, with difficulty, cured. If 
the fault be in the soil it must,” he says, “ be 
dug out and fresh mould put in its place ; 
or, the trees must be taken up, and others, 
better adapted to the soil, planted in their 
room. It will be found absolutely neces- 
sary always to endeavour to suit the parti- 
cular sorts of fruit to the nature of the soil ; 
for it is in vain to expect all sorts of fruit to 
be good in the same soil. If the weakness 
of the tree proceed from an in-bred distem- 
per it will be adviseable to remove it at 
once, and after renewing the earth to plant 
another in its place.” But if the weakness 
is brought on by ill management in the 
pruning, which is frequently the case, he 
would advise more attention to the method 
of pruning and training. Besides this, 
f ‘ there is another sort of blight that some- 
times happens pretty late in the spring, as 
in April or May, which is very destructive 
to fruit trees in orchards and open planta- 
tions, and against which we know of no 
effectual remedy. This is what is called a 
fire-blast, which, in a few hours, hath not 
only destroyed the fruit and leaves, but 
often parts of trees ; and sometimes entire 
trees have been killed by it.” As this gene- 
rally happens in close plantations where the 
vapours from the earth and the perspiration 
from the trees are pent in for want of a free 
circulation of air to disperse them ; it points 
out to us the only way yet known of guarding 
against this enemy to fruits ; namely, to make 
choice of a clear healthy situation for kit- 
chen-gardens, orchards, &c. and to plant the 
trees at such a distance as to give free ad- 
mission to the air, that it may dispel those 
vapours before they are formed into such 
volumes as to occasion these blasts.’’ But 
blasts may also be occasioned by the reflec- 
tion of the sun’s rays from hollow clouds 
which sometimes act as burning mirrors 
and occasion excessive heat. See Aphis. ’ 
BLINDNESS, a total privation of sight 
arising from an obstruction of the functions 
of the organs of sight, or from an entire de- 
privation of them. 
, This defect may arise from a variety of 
causes, existing either in the organ of sight 
or in the circumstances necessary to pro- 
duce yision. Blindness will be complete 
when the light is wholly excluded ; or par- 
tial, when it is admitted into the eye so 
imperfectly as to convey only a confused 
perception of visible objects. Blindness 
may again be distinguished into periodical 
or permanent, transient or perpetual, natu- 
B LI 
ral or accidental, &c. ; but these distinc- 
tions do not serve to communicate any idea 
of the causes of blindness. 
We find various recompenses for blind- 
ness, or substitutes for the use of the eyes, 
in the wonderful sagacity of many blind 
persons, recited by Zahnius, in his “ Ocu'.us 
Artificialis,” and others. In some, the de- 
fect has been supplied by a most excellent 
gift of remembering what they had seen ; 
in others, by a delicate nose, or the sense of 
smelling; in others, by an exquisite touch, 
or a sense of feeling, which they have had 
in such perfection, that, as it has been said 
of some, they learned to hear with their 
eyes; as it may be said of these, that they 
taught themselves to see with their hands. 
Some have been enabled to perform all 
sorts of curious and subtle works in the 
nicest and most dexterous manner. 
Aldrovandus speaks of a sculptor who 
became blind at twenty years of age, and 
yet, ten years after, made a perfect marble 
statue of Cosmo IT. de Medicis; and an- 
other of clay like Urban VIII. 
Bartholin tells us of a blind sculptor in 
Denmark, who distinguished perfectly well, 
by mere touch, not only all kinds of wood,’ 
but all the colours; and F. Grimaldi gives 
an instance of the like kind ; besides the 
blind organist, living in Paris, who is said 
to have done the same. The most extraor- 
dinary of ail is a blind guide, who, accord- 
ing to the report of good writers, used to 
conduct the merchants through the sands 
and desests of Arabia. 
James Bernouiiii contrived a method of 
teaching blind persons to write. 
An instance, no less extraordinary, ; s 
mentioned by Dr. Bew, in the “ Transac- 
tions of the Manchester Society.” It is 
that of a person, whose name is John Met- 
calf, a native of the neighbourhood of Man- 
chester, who became blind at so early an 
age as to be altogether unconscious of light 
and its various effects, His employment in 
the younger period of his life was that of a 
waggoner, and occasionally as a guide in in- 
tricate roads during the night, or when the 
common tracks were covered with snow. 
Afterwards lie became a projector and sur- 
veyor of highways in difficult and moun- 
tainous parts ; and, in this capacity, with 
the assistance merely of a long stafi', he tra- 
verses the roads, ascends precipices, ex- 
plores valleys, and investigates their several 
extents, forms, and situations, so as to an- 
swer his purpose in the best manner. His 
plans are designed, and his estimates form- 
