The Lord Ordinary may grant commission in any action—
(a)to any person competent to take and report in writing the depositions of havers;
(b)to take and report in writing the evidence of any witness who is resident beyond the jurisdiction of the Court, or who, by reason of age, infirmity or sickness, is unable to attend the diet of proof or trial:
Provided that nothing in this section shall affect the existing practice in regard to granting commission for the examination of aged and infirm witnesses to take their evidence to lie inretentis before a proof or, as the case may be, trial has been allowed.