VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 56g 



Fig. 1'2 a cover to fig. 1 1 : a, a, the body, fitting exactly over, and b the cup-part (holding 3 oz.), 

 fitting exactly within, tlie corresponding parts of fig. 11. 



Fig. 13 the instrument for grinding the ice into powder ; it works on a short centre point, and has 

 the edge bevilled contraryways ou each side the point, so as to follow. The fineness of the powder 

 is regulated by the degree of pressure used. The handle is wood, the rest metal : a is a sliding 

 cover, fitting on the tube in which the ice is ground, to exclude the external air, and to keep the 

 instrument steady ; b is the shoulder or guard, to prevent the point of the instrument fiom touching, 

 so as to endanger injuring the bottom of the tube. It should be made so as to fit, without grating 

 the inside of the tube in using. The tubes of each of the vessels should be somewhat shorter than 

 the vessel, so as not quite to reach the bottom of it. 



Fig. 14 a thermometer glass, with the bulb | full of quicksilver. 



Fig. 15 a thermometer with the lower part of the scale-board turned up with a hinge, for the con- 

 venience of taking the temperature of small quantities, or of mixtures in which mineral acids form 

 a part. 



XIK Observations on the Grafting of Trees. By Thomas Andrew Knight, Esq. 



p. 290. 



The disease from whose ravages apple and pear trees suffer most is the canker, 

 the effects of which are generally first seen in the winter, or when the sap is first 

 rising in the spring. The bark becomes discoloured in spots, under which the 

 wood, in the annual shoots, is dead to the centre, and in the older branches, to 

 the depth of the last summer's growth. Previous to making any experiments, I 

 had conversed with several planters, who entertained an opinion, that it was 

 impossible to obtain healthy trees of those varieties which flourished in the be- 

 ginning and middle of the present century, and which now form the largest 

 orchards in this country. The appearance of the young trees, which I had seen, 

 justified the conclusion they had drawn; but the silence of every writer on the 

 subject of planting, which had come in my way, convinced me that it was a 

 vulgar error, and the following experiments were undertaken to prove it so. 



I suspected that the appearance of decay in the trees I had seen lately grafted, 

 arose from the diseased state of the grafts, and concluded, that if I took scions 

 or buds from trees grafted in the year preceding, I should succeed in propagating 

 any kind I chose. With this view I inserted some cuttings of the best wood I 

 could find in the old trees, on young stocks raised from seed. I again inserted 

 grafts and buds taken from these on other young stocks, and wishing to get rid 

 of all connection with the old trees, I repeated this 6 years; each year taking 

 the young shoots from the trees last grafted. Stocks of different kinds were 

 tried, some v/ere double grafted, others obtained from apple-trees which grew 

 from cuttings, and others from the seed of each kind of fruit afterwards inserted 

 on them; I was surprized to find that many of these stocks inherited all the 

 diseases of the parent trees. 



The wood appearing perfect and healthy in many of my last grafted trees, I 



VOL. XVII. 4 D 



