November 11, 1921] 



SCIENCE 



469 



tion. These surprising disclosures led to an 

 examination of a number of text-books, etc., 

 on sound, from whieli it appeared that only 

 rarely was there any reference to the true 

 theory of the fork; even the Britannica sup- 

 ports the view of the psychologist. So a note 

 on the subject may not be superfluous. 



The theory of the fork is due to Chladni's 

 researches of a century ago. He had found 

 that a horizontal straight uniform bar could 

 vibrate when supported at points about 0.22 

 of its length from the ends; obviously por- 

 tions each side of these nodal points must at 

 any instant be moving in opposite directions. 

 Then he bent the bar a little and found that 

 the nodes had moved toward the center, and 

 when the fork-shape with long parallel prongs 

 was reached, the nodes were near the base 

 of the prongs. Assuming the prongs vertical, 

 when they separated the intermediate part 

 near the bends would of course rise a minute 

 distance. In any practical case the center 

 portion is loaded by the stem which will 

 therefore move up and down and deliver 

 regular blows to a sounding board or reso- 

 nance box on which it may be placed. Such 

 an effect can not be accounted for by the 

 crude theory that prompted this note. 



It will help to clear thinking to recall the 

 curious fork shown by the Standard Scientific 

 Co. at the exhibit of apparatus at the Bureau 

 of Standards about a year ago. This had 

 a relatively large hole near the upper end of 

 the stem, the effect of which was to make 

 the pitch much lower than that of a similar 

 fork unperforated. 



In this connection it may be added that 

 measures I made some years ago showed that 

 a Koenig's fork of the middle octave on its 

 box, when vibrating at an average amplitude, 

 expended its energy at the rate of about one 

 millionth of a horse power or less than a 

 thousandth of a watt; of course only a small 

 part of this produces sound and only a very 

 minute fraction of this part could reach the 

 ear of any one of the hundred who could 

 hear the fork. 



Charles K. Wead 



Ann Aebor, Mich. 



SPECIAL ARTICLES 



THE RELATION OF SOIL FERTILITY TO VITA- 

 MINE CONTENT OF GRAIN i 



This study was undertaken at the sug- 

 gestion of Professor F. J. Alway, who has 

 made a study of the relation of phosphate- 

 hungry peat soils to the grain produced on 

 them,^ at G-olden Valley, Minn. 



Burning of the peat rendered mineral mat- 

 ter more available to the plant and increased 

 the yield. It also increased the amount of 

 phosphoric acid in the grain and, as we shall 

 show, increased the vitamine. Two experi- 

 ments were made, one with barley grown on 

 untreated and on burned peat, and another on 

 oats grown on peat soil as contrasted with 

 ordinary mineral soil. The barley grown on 

 untreated peat yielded 7.4 bushels per acre 

 and the grain contained 0.5 per cent. P^O^ in 

 the dry matter, or 17.9 per cent, in the ash, 

 whereas the barley grown on burned peat 

 yielded 42.6 bushels per acre and contained 

 1.06 per cent. PjO^ in the dry matter and 

 35.5 per cent, in the ash. The oats gro^vn on 

 untreated peat soil contained 0.52 per cent. 

 T„0^ in the dry matter and 17.9 per cent, in 

 the ash. The oats grown on ordinary mineral 

 soil in the same locality contained 1.1 per 

 cent. PjOj in the dry matter and 32.4 per 

 cent, in the ash. It was at first attempted to 

 determine the vitamine content of these grains 

 by the quantity necessary to prevent or cure 

 polyneuritis in pigeons. It was very difficult, 

 however, to feed these grains quantitatively to 

 these pigeons, and they all died of polyneuritis 

 before the end of the experiment. 



The next attempt was to feed the whole 

 grains quantitatively to white rats, but this 

 method failed also. 



The next method was to grind the grains 

 and mix them to the extent of 5 per cent, in a 



1 Contribution from the laboratory of physio- 

 logical chemistry. University of Minnesota Medical 

 School. 



2 F. J. Alway, ' ' A phosphate-hungry peat soil, ' ' 

 Journal of the American Peat Society, Vol, 8, 

 1920. 



