What fire is
Barrington, Ill.
Dear St. Nicholas: Will you please tell me what “fire” is?
Lucile G. Robertson.
Fire, as we usually see it, is the action of air upon hot substances that can burn. It is only one ingredient or part of the air which does this, the oxygen. Usually when things burn, there are hot gases and vapors formed which make the flame. Fire is not a substance, therefore, but an action, or its appearance. Most things that can burn in the air can do so only when heated very hot, but since the burning of a part of the thing produces much heat, a fire will often increase and spread enormously. Three things are needed, then, to make a fire: sufficient heat to start it, a supply of the thing that will burn, and a supply of air. Water puts out fire because it cools the thing that is burning, or covers it up, and keeps the air away.—Professor H. L. Wells, New Haven, Connecticut.
The speed of birds in flight
Broadrun, Va.
Dear St. Nicholas: Will you please tell me which can fly swiftest, the wild duck, the hawk, or the pigeon? And which bird can fly swifter than any other in the world?
Yours very truly,
Cassius C. Dulany (age 12½).
Two observations with scientific instruments give to migrating ducks a speed of forty-seven and eight tenths, and to migrating geese a speed of forty-four and three tenths, miles per hour. Homing pigeons do not exceed forty to forty-five miles an hour. Doubtless all three birds can fly much more rapidly, but I know of no exact observations which would tell us of the utmost speed they have attained or might reach.—F. M. Chapman, Curator of Birds, American Museum of Natural History.
Why a nasturtium leaf looks silvery under water
Villa Fontanelle, P. Ovile, Siena, Italy
Dear St. Nicholas: Will you please tell me why, putting a nasturtium leaf under the water, it looks as if it was of silver? Egle Bossi.
The nasturtium leaf is covered with a finely distributed, waxy substance which will not permit water to wet the leaf. Hence, when immersed, the water cannot touch the leaf and drive off the air surrounding it, and a thin layer of air remains between the leaf and the water. It is the reflection and refraction of light from this layer of air that give the silvery appearance. It has been supposed by some authorities that the presence of this non-wettable layer has the advantage of preventing the raindrops which fall on the leaf from remaining there, and thus blocking up the stomata, or breathing-pores.—W. F. G.
A very small beech-tree bearing a nut
(From one of our adult readers)
Chicago, Ill.
Dear St. Nicholas: While tramping in the woods in northern New York State, I found the accompanying beech twig, or sucker, with a single fruit on its tip. It was growing about eight feet from the main trunk on the root of a large tree, somewhat as shown in my rough sketch.
The root was exposed where the sucker grew. While this may not be an unusual occurrence, I had never seen such a growth on any other tree. The parent tree bore a heavy crop of nuts, but the nut on the sucker was smaller and less perfectly developed than those on the parent tree.
In order to make a perfect proof I should have cut a 
A tiny beech growth from a root bearing nut burs. small piece from the surface of the root to which the twig was attached, but I did not think of doing so until too late.
This unusual growth may possibly be of interest to the nature lovers who read the “Nature and Science” department of St. Nicholas.
I have been a reader of St. Nicholas since its first issue, in 1873, I believe, and to-day, when it comes to our home, I read the nature department first. I am,
Very sincerely,
Orpheus M. Schantz.
This is, indeed, a remarkable example of a small tree bearing fruit. It makes one think of Luther Burbank’s experiments with very small chestnut-trees producing a large crop of full- sized burs and nuts.—E. F. B.
