74 EXPERIMENT STATION EECOED. 



concerning the effects of dips on tensile strength. To see if the relation between 

 breaking strain and diameter of fiber was more reliable 1,000 fibers of a Penn- 

 sylvania half-blood sheep were tested. The means of the separate hundreds 

 gave an average breaking strain of 6.769 gm., the diameter of the fibers being 

 22.17^. From the results obtained it is concluded that the breaking strain is 

 more nearly proportionate to the diameter than, as might be supposed from the 

 laws of mechanics, to the square of the diameter. 



A series of calculations w^as made to determine the number of tests necessary 

 to give the tensile strength of a sample of wool with sufficient accuracy for the 

 dip studies by using the standard deviation of the sample as a basis on which to 

 calculate the probable error for any given number of tests. From the tabulated 

 data " it can be seen that the reliability of the approximate mean as compared 

 to the true mean, which is shown by the decrease of the probable error, increases 

 quite rapidly from 100 to 700. This increase in reliability is relatively slower, 

 showing that there is very little gain in reliability by increasing the number of 

 tests to above 700. Since, however, it Is better to test too many than too few, 

 and since 1,000 is a very convenient number to use In making calculations, it is 

 quite probable that 1,000 [fibers] will be the number used unless further experi- 

 ments show that some other number is better." 



Both the breaking strain and the diameter of each fiber should be measured, 

 " but taking into consideration the fact that it requires more than twice as 

 much time to measure both the breaking strain and diameter as it does to meas- 

 ure only the former, it is plain that it is more economical to test 1,000 fibers for 

 the breaking strain alone than to test 600 for both." 



A laboratory method of scouring wool. A, E. Vinson and W. H. Ross 

 (Arizona Sta. Rpt. 1908, pp. 367-310). — The authors advise a preliminary wash- 

 ing in clear water when the amount of sand and dirt is to be determined. The 

 stock scouring solutions recommended are much weaker than those ordinarily 

 used by wool scourers. The method, which is described in detail, gave lower 

 results than the tub method of using the whole fleece. 



" From these results it appears that the yield of pure dry wool by the labora- 

 tory method, using a small sample, corresponds closely with that obtained by 

 scouring the whole fleece with the same solution," 



Pork production at the Delta station, J. W. Fox (Mississiirpi Sta. Bui. 107, 

 rev. ed., pp. 7). — To this revised edition (E. S. R., 19, p. 1170) is appended a 

 brief note of experiments on the value of peas for pork production and as a 

 fertilizer when planted in corn at the last working. 



" After the corn was gathered, 51 spring pigs were turned into the pea field 

 of 17 acres. They had no additional feed. The gain made from the peas was 

 2,893 lbs., or 170 lbs. per acre. At 6 cts. per pound, this gives a value for the 

 peas of $10.20 per acre. And this is net, as the hogs did their own harvesting. 

 Also the manure and humus from stalks, vines, and seed were left on the land. 

 By tests made at the station for two years to determine the value of peas 

 grown in corn, as a fertilizer, it has been found that they increase the suc- 

 ceeding cotton crop by 110 pounds of lint per acre. The land used was old 

 and had been cropped continuously in cotton. A prolific short variety of cotton 

 was used in the test. Figuring the increase at 9 cts. per pound, the peas had a 

 fertilizing value of $9.90 per acre. The above eloquently suggests a means of 

 improving our lauds, worn by a one-crop system, at a profit instead of an 

 expense." 



Poultry problems and profits, W. L. Nelson {Missouri Bd. Agr. Mo. Bui., 6 

 (1908), No. 12, pp. 52, figs. 16, dgms. .',).— This bulletin was prepared for the 

 use of those interested in practical poultry culture. The information contained 



