On a Disease hi Elm Trees. 383 



We have seen several of the affidavits alluded to, on both 

 sides of the question, conversed with four of the deponents, 

 and examined the trees. Most of the depositions proceed on 

 the supposition of the gas escaping from the pipes under 

 ground, and being absorbed by the vessels of the roots; but 

 one argues on the idea of the gas escaping in the atmosphere, 

 and acting by contact with the parts injured. Some of the 

 deponents, as Mr. Lindiey, reason on physiological princi- 

 ples ; others, as Mr. Sinclair, from experience and observ- 

 ation ; a third class decide empirically ; and one gentleman 

 experimentally. This last deponent, an eminent chemist, 

 planted some sets of potatoes in natural soil, and some in soil 

 impregnated with hydrogen gas, and found that those in the 

 latter soil were some days later in appearing above ground 

 than the others; however, they did appear, and grew very 

 well. 



That plants, like animals, may be poisoned by the absorption 

 of deleterious substances, has been proved by M. T. Mar- 

 cet (Gard. Mag. 89.): but that the disease in the bark of 

 these elms is not owing to the absorption of poison, Mr. Lind- 

 iey has satisfactorily deduced from the known facts, that the 

 sap absorbed by the root of a tree ascends by the wood to the 

 leaves, and there being changed into proper juice, analogous 

 to the blood of animals, returns by the bark ; consequently, 

 in returning, it would first have affected the young shoots at 

 the top of the tree, and on the extremities of the branches, 

 before it could have injured the lower part of the trunk. 

 That the disease is not owing to the presence of gas in the 

 atmosphere is evident from the circumstance of neither the 

 leaves of the elms, nor the flowers and tender shrubs close to 

 that side of the road where the gas pipes are laid, being in 

 the slightest degree injured. What, then, is the cause of the 

 disease ? Old age and the want of nourishment. This is our 

 decided opinion. The soil is thin, on a gravelly subsoil ; the 

 trees stand close together, and, consequently, the ground is 

 completely filled with their roots. Already stinted in their 

 growth, and beginning to decay, this process was accelerated 

 by the dry summer of 1825, and by a series of excavations 

 made in that year along one side of the avenue for a row of 

 houses ; which completely drained the gravelly stratum. 



The extravasation of the juices mentioned by Mr. Lindiey, 

 did not appear to us general, and the insects alluded to by our 

 correspondent are found under the bark of most elm trees in 

 a state of decay, and are to be considered as the consequences 



d d 3 



