The death of trees in cities is frequent and the stereotyped diagnosis is "gas." That gas will destroy trees I doubt not. Illuminating gas is of less specific gravity than air, and if escaping under ground should rise through it. It is not absorbed by water and should not thus be retained in the soil to the material detriment of the trees. Escaping gas in the presence of the entire root-system of a tree would likely kill it, but the destruction of part of the roots, or the application of destructive agents to a part only of the roots of a tree would not in my observation do further harm than check the growth in proportion to the injury sustained.

I have seen many trees perish in the city and have often wondered that tree-life was at all possible. With an impervious stone covering, with no possibility to cultivate or aerate the soil, and with the continuous application of waste slops containing all manner of injurious substances, it is, indeed, wonderful that plant-life is at all possible.

In Lexington I also notice the loss of which your Louisville correspondent complains. But the cause of the injury is not due to gas. The streets have recently been supplied with water mains and the trees on the sidewalks have been severely root-pruned. The weather in Kentucky has recently been extremely hot, and at Louisville very dry. Here we had abundant rain-falls - nearly 11¾ inches during June and July - but before the window at which I write stands a vigorous young sugar maple that on the morning of July 21st was the picture of robust life, and in the evening the leaves on the southwest side might have been used for kindling. The soil was moist and covered with luxurious sod, but with the thermometer on a shaded north portico at 990, the tree yielded to the open heat of the sun, intensified by reflection and radiation from the contiguous building.

It is this latter condition that destroys trees in cities. The soil rarely dries, but the pent heat, intensified by radiation and reflection, removes moisture faster than the roots can supply it. I notice many trees in Lexington assuming a yellow unhealthy hue, but it is due to root-pruning and to heat, intensified by the surroundings. Some will perish, but the lengthening nights and diminishing heat will mitigate the injury. Lexington, Ky.

[Coal gas, as our correspondent well remarks, is lighter than the atmosphere, and must be pushed up out of the ground when air or water forces its way in; and yet, if he has dug up trees killed by coal gas, as they certainly are, he will find the newly turned up earth so nauseous with the stench that he would certaintly be convinced that something has been retained, though the mere "gas" has escaped.

The conditions referred to by our correspondent undoubtedly injure and kill trees sometimes; and yet there can be no more reason to doubt that gas kills trees also, in the mind of anyone who has lived in Philadelphia a few years, than that lightning also sometimes kills them. If it were desirable we could give in detail evidence that would satisfy anyone. This evidence is not merely of the "popular kind" that "knows such and such is the case because it is," but the facts have been carefully gone over by scientific experts. We need only name here a paper by B. A. Fahnestock, one of Philadelphia's leading chemists, who, a quarter of a century ago, published in the Proceedings of the Academy of Natural Sciences of Philadelphia, with elaborate details of his experiences. - Ed. G. M].