It mny be nrgued thnt, since it lins been shown thnt for mnny mnterinls, the flow properties nppenr to he extremely complex,0 nny trentment which clnims to express all these complesities in terms of only three or four constnnts of tlie mnterinl must he no over-simplificntion. It is likely that pnrt of the supposed complexities arose from the pnrticulnr manner in which the dntn wcre trented, ix., by the nrtificinl attempt to relnte all the phenonienn in n summntion of elnstic nnd viscous terms. There is, however, the possibility thnt the older nnnlyticnl methods by which strnins ore nrbitrnrily divided into recovernble nnd non-rccovernble pnrts will still need to he used to study certnin specific phenomenn, but there is n danger, \vell-known in psychology, that in too detailed nn nnnlysis, lve lose mnny of the properties of the intcgrntcd whole.It should be einphnsised thnt the fnct thnt the trentment nppenrs to work equnlly well in tension, compression, and (ns Broome nnd Bilmes hnve shown) in torsion does not imply that the vnlues of log +, k, ete. are necessnrily tho snme when n mnterinl is strnined in these three different w y s . This is by no nienns so ; in fnet, in the cnse of printing fiongs, the vnlues of b vnry depending on whether tho extensions are carried out dong or across the test-piece which is known to be nnisotropic.
SUY3fARY(1) An equntion originnlly proposed by Nutting, but appnrently unused for ninny yenrs, has .been re-derived from nltogether new considerntions in order to relnte stress, strain, and time in the strniniug of soft mntcrinls.(2) This equation is linked with psycho-physienl studies published elsewhere nnd describes the properties of the mnterinls in terms of three or occnsionnlly four constnnts which nre npproximntely independent of stress or strnin conditions over n considerable range.(3) Esperiments nre described in which cylinders of mnny indnstrinl mnterinls ore compressed under constnnt stress (incrensing totnl lond). These ninterinls show mnny complex properties, such ns work-hnrdening, fnlsebody, structurnl viscosity, nnd dilntnncy, but, with very few exceptions, tlie proposed trentment gives simple and relinble results.. (4) The proposed equntion is being used with succcss by n number of other workers, using very different materials, in torsion nnd cstcnsioii instend of comprcssion. Although by no nienns of universnl validity for soft mnterinls, it is suggested thnt the trentment has n very genernl npplicntiou nnd thnt tlie !,ink with the concepts used in judging the "firmness of mnterials subjectively by hnndhig glres this trentment some sdvnntnge over tho older methods.
Chemistry Depnrtment,Both tho conventional methods of determining nitrogen in orgnnic materinls, tho Dumns mothod of burning the mntcrinl in contnct with comer oxide in n strenm of cnrbon diosido nnd tho Kjeldnlil ine'tihotl of decomposing it by menns of sulohurio ncid. hnrc their disndmntnecs ns customnrily p'rnotised. IIy rcdriciiig tho ~nnterinl,~if tlrc iiitrogen is linked to osygen, beforo submittin...
