THE SECRETARY'S PORTFOLIO. 397 



ords preserved in his family renching back to the Spanish settlement of that 

 territory — more than two hundred and fifty years ago — show indisputably that 

 its forestry, rainfall, and general climatic features are unchanged. Also while 

 in Mexico I was informed by Governor Tarasscs ol' Chiluiahua, that the same 

 has been true of his country since its earliest historical times, but that there 

 appears to be periods, ranging from twenty-five to illty years, in wiiich the 

 character of the seasons, as to moisture, temperature, etc., has fluctuated 

 between the limits of certain extremes. It is true tree culture there has been 

 almost wholly confined to the gardens of the Jesuit lathers, and along the 

 banks of the Acequias, and sustained by irrigation. But the lact that large 

 areas had been irrigated and agriculture maintained for centuries, should have 

 produced by this time at least some discernible modifying climatic results. On 

 the contrary these elevated plateaus, lying between parallel mountain ranges 

 in interior Mexico, present fixed climatic conditions, and no human endeavor 

 will ever change them. The mountain chains bordering those plateaus and 

 nearest the coast lines — the Pacific particularly — arrest the moist wind currents 

 and are abundantly supplied with rain and snow. Hence it happens that those 

 mountains are clad with natural forests, and agriculture among their foot-hills 

 and along their base is such as normal and sufficient rainfall supports. The 

 flora, too, of all those vast arid sections, presents incontrovertible evidence on 

 this point, and is, of course, far more valuable and convincing than any merely 

 traditional or historical testimony. 



TREE PLANTING BY RAILROAD COMPANIES. 



The following is a brief abstract of a paper read by Dr. Franklin B. Hough, 

 of Lowville, N. Y., before the American Forestry Congress: 



We have now^ about 100,000 miles of railroads in the United States. Allow- 

 ing nothing for increase, but making estimates on the present lines, in the 

 matter of ties, the figures would run something as follows: The number of 

 ties per mile ranges Irom 2,200 to 3,000, and in some cases as high as 3,500. 

 If we assume that they average 2,500 to the mile, we have a quarter of a billion 

 in use. They average eight feet in length, and about seven inches deep and 

 eight wide, giving the contents about three cubic feet a])iece, or in all six 

 millions of cords. If piled cord fashion, they would form a pile four feet high, 

 eight feet wide and 4,575 miles long. Placed end to end they would span the 

 earth fifteen times at the equator, or in one line would reach miles beyond the 

 moon. We may take their average life at from five to eight years, and we 

 shall need from 30,000,000 to 50,000,000 new ties a year for maintaining the 

 present railroads of the country in constant use. 



The number of ties that can be cut from an acre of wood land varies exceed- 

 ingly, but, at 500 to the acre, we shall need to cut over from G0,000 to 100,000 

 acres every year, to meet this demand. 



It probably is not out of the way to say that trees will grow from seed to 

 size sufficient for ties in thirty years; then we shall need from nearly two 

 millions to over three millions of acres, or from 3,12(1 to 4,687 square miles of 

 forest to keep up this supply. 



At the rates we have assumed, there should be from eighteen to thirty acres 

 of woodland for every mile of single track road. Taking twenty-five as a safe 



