36 REPORT— 1867. 



experiments, the nictliod of least squares, we fiud for A^ B, and C the following 



values : — 



A= -0-13259174 with mean probable errors for A=4-0-0152094G 

 B= +4-21442268 with mean probable errors for B= +0-01393995 

 C = - 0-01982625 with mean probable errors for C = +0-00283004. 



These values of A, B, and C being put in the equation « = 0, give us the two nume- 

 rical expressions of P, which render the coefficient of absorption equal to zero, 

 namely, P = 0-109 atm. and P = 6ri44 atm. At the same timewe see that a, becomes 

 a maximum for P=:30-66 atm., and that for this pressure it will be nearly 18 times 

 greater than when P = 1. The value of P = 61 atm. is evidently the pressure required 

 for the liquefaction of carbonic acid gas at the temperature of 15° C, and we have 

 no direct experiments for the verification of this number ; but if we take the ob- 

 servations of M. Regnault on tlie points of ebullition of liquid carbonic acid gas at 

 different pressures, we obtain the following Table : — 



Difference m i. -n • j. Difference 



„■" "; Temperatm-e. Press, ni atm. r. 



of temperature. ^ ot pressure. 



iP°, — 73-3G 1-8 ^.r- 



-IC\.'7 — "U ' '> •> r..Q 



}?? -400 11-1 'il 



ll'l r.o.n l,;.o 2 



16'7 —^:i J .^ 10-5 



If we calculate by means of this Table the pressure necessary to liquefy carbonic 

 acid gas at the temperature of 15"^ C, we obtain exactly the number 61-1 atmo- 

 spheres. 



Without attaching more importance than they deserve to the above-mentioned 

 numerical expressions of A, B, 0, and a. and P maxima, Szc, which cannot be strictly 

 exact, as being concluded from a too limited series of experiments, I have mentioned 

 them onlv for showing that our method of experimentation can give us, in a com- 

 paratively easy way, — 



1st. The values of pressure required for the liquefaction of gases ; and, 

 2ndlv. The numerical Aalue of the maximum of absorption of every gas, vary- 

 ing only with the nature of the gas and Avitli the temperature. 



Preliminary Notice of Results on the Composition of Wheat groivn for twenty 

 i/ears in succession on the same Land. By J. B. Lawes, I'^.Ii.S., F.O.S., and 

 J. H. GiLBER-r, Ph.D., F.R.S., F.C'.S. 



These results had reference to the produce of a field in which wheat had now 

 been gi-own, on some plots without niautn-e, on one with farm-3-ard mantire, and 

 on others by different artificial mixtures, for twenty-four years in succession 

 (1843-4 to 1866-7 inclusive). At the Cheltenham Meeting of the British Asso- 

 ciation in 1856, the authors treated of the effects of season and manures on the 

 composition of thw crop as illustrated by the results of analysis relating to the 

 .roduce of some of the plots during the first ten years of the experiments*. At the 

 lancliester Meeting, in 1861, they recurred to the subject; the analytical results, 

 wliicli then extended to the produce of some of the plots for sixteen years, were, 

 however, chieflv applied to the illustration of certain points in connexion with the 

 exhaustion of soils. At the Nottingham JNIeeting, in 1866, they treated of the 

 acciunulation of the nitrogen of manure in the soil of the same experimental field. 

 The restdts adduced on the present occasion showed the eftects of season and 

 manuring on the composition of both the gi-ain and the straw during twenty years 

 of the experimental growth. 



The particulars of composition given are— the percentages of dry substance, 

 of mineral matter, and of nitrogen, and the constituents of the ash of both grain 

 and straw, more than 200 complete ash-analyses being brought to bear on the 

 subject; and, side by side with these, as indicating the general characters of the 



* " On some points in the Composition of Wheat-grain, its products m the Mill, and 

 Bread," Juurn. C'liem, Soc. vol. x. 



I 



