Mr W. S. Macleay on the State of the Elm Trees , 4*c. 123 
white. When trying to find nickel, it seemed to contain 7 to 8 
per cent. 
Zipaquira, in the limits of which these last masses were found, 
is in Lat. 4° 57' N., and Long. 76° 33' W. of Paris. Its eleva- 
tion above the level of the sea is 265 0 metres *. 
Art. XII . — Abstract of a Report on the State of the Elm 
Trees in St James's and Hyde Parks. Drawn up at the 
request of Lord Sidney, the Ranger, for the Treasury, by 
W. S. Macleay, Esq, A. M. F. L. S. &c. &c. 
[The following remarks compose the substance of a Report on the 
State of the Elm Trees in St James’s and Hyde Parks, which 
was lately drawn up at the request of Lord Sidney the Ranger, 
in order to be presented to the Treasury. As it is possible that 
some of your readers may have trees affected in a similar manner, 
perhaps a communication on the subject may not be deemed 
unworthy of a place in the pages of the Edinburgh Philosophi- 
cal Journal. I have the honour to be, &c. 
To Professor Jameson. W. S. Macleay.] 
So little attention has hitherto been paid to the causes of dis- 
ease in trees, that few persons ever think of attributing it to any 
other origin than one entirely vegetable, or, in other words, to 
the constitution of the plant itself. Yet, in every case, perhaps, 
where the disease is infectious, and particularly where it is con- 
fined in a plantation or forest to the individuals of one species 
of tree, we may reckon with certainty on its proceeding from the 
attacks of some insect. Every tree, nay, indeed, every plant 
seems to have one or more species of insect destined by Nature 
to feed on it ; and when, from the combination of various causes 
(such, for instance, as the weakness of vegetation in a particular 
air or soil, inattention to the evil at the proper time for effec- 
tually checking it, & c.), the number of insects which attack trees 
* Mr Rivero, in his original memoir, chooses to name these masses 1 Problema- 
tical Irons,’ at the same time proving them to be meteorical ; and undoubtedly 
they differ in no essential respect from those we have seen, and possess, from Tu- 
cuman, in the province of Buenos Ayres, from Mexico, Brazil, and many other 
places. — IIculand. 
