20 NOVEMBER 1926, Page 15

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The methods of tree surgery now used by the Government and by municipal bodies both in the United States and in Canada is almost an exact imitation of the dentist's art. The inci- pient hollow is sought out, if need be by the microscope ; when found, it is cleaned out till not an atom of caries is left ; then and not till then the cavity is filled up. The art, which Is associated with the name of " The Davey Institute of Tree Surgery," perhaps owes something to deliberate imitation of the dentist ; and like the dentist the tree surgeons have been especially active in experimenting with the best material for filling the hollows. The victory seems to have been won. not by gutta-percha or even gold, but by Portland cement. It is no little satisfaction to know that if we have a favourite

tree or two we can extend its age perhaps for a century by digging holes round it and filling up those in its own middle. If anyone particularly wishes to see how careful of these trees English county-house dwellers may be, let him walk among the huge antique oaks of Hatfield Park. Some of them are in splints and some look as if they might hobble towards you on their crutches.