THE LONGEVITY OF TREES. 17 
houses,’ in 1805, and on ‘ Country Residences,’ in 1806, both 
4to; ‘Hints on the Formation of Gardens,’ in 1812; and 
three works on ‘ Hothouses,’ in 1817 and 1818. In 1822 ap- 
peared the first edition of the ‘ Encyclopedia of Gardening’ ; 
a work remarkable for the immense mass of useful matter 
which it contained, and for the then unusual circumstance - of 
a great quantity of woodcuts being mingled with the text: 
this book obtained an extraordinary sale, and fully established 
his fame as an author. Soon after was published an anony- 
mous work, written either partly or entirely by Mr. Loudon, 
called the ‘ Greenhouse Companion’; and shortly afterwards, 
‘ Observations on laying out Farms,’ in folio, with his name. 
In 1824, a second edition of the ‘ Encyclopedia of Garden- 
ing’ was published, with very great alterations and improve- 
ments; and the following year appeared the first edition of 
the ‘ Encyclopedia of Agriculture.’ In 1826, the ‘ Gardeners’ 
Magazine’ was commenced, being the first periodical ever de- 
voted exclusively to horticultural subjects. The ‘ Magazine 
of Natural History,’ also the first of its kind, was begun in 
1828. Mr. Loudon was now occupied in the preparation of 
the ‘ Encyclopedia of Plants,’ which was published early in 
1829, and was speedily followed by the ‘ Hortus Britannicus.’ 
In 1830, a second and nearly rewritten edition of the ‘ Ency- 
clopedia of Agriculture’ was published, and this was followed 
by an entirely rewritten edition of the ‘ Encyclopedia of 
Gardening,’ in 1831; and the ‘Encyclopedia of Cottage, 
Farm, and Villa Architecture,’ the first he published on his 
own account, in 1832. This last work was one of the most 
successful because it was one of the most useful he ever wrote, 
and it is likely long to continue a standard book on the sub- 
ject of which it treats. Mr. Loudon now began to prepare 
his great and ruinous work, the ‘ Arboretum Britannicum,’ 
the anxieties attendant on which were, undoubtedly, the 
primary cause of that decay of constitution which terminated 
in his death. This work was not, however, completed till 
1838, and in the mean time he began the ‘ Architectural 
Magazine,’ the first periodical devoted exclusively to archi- 
tecture. The labor he underwent at this time is almost in- 
