would be about one millibarn if the scattering were largely inelastic or elastic and isotropic. The effect otherwise could be much larger depending on the real parts of the neutron and proton forward scattering amplitudes, which are unknown.From the attenuation of the E^O target we obtain for the total K + -oxygen cross section (for absorption and diffraction scattering) at 0.69 Bev a value of 270 ±20 mb which is 90% of geometric.The K -proton total cross section was measured at 0.96 and 1.23 Bev with the result 36 ± 5 and 44 ± 5 mb, respectively. From the decay in flight we obtained the lifetime r^+ = (1.21 ±0.06) xlO" 8 sec in good agreement with previous measurements on stopped K's. By this method we measured the ratio of K" to K+ lifetime directly and got T#-/T# + = 0.97 ±0.09.We note the following: (a) The JC + -proton total cross section reaches a maximum of 4ir(fi/m K c) 2 or about 7r(S/2m ff c) 2 at P Q m * -m^c; i.e., a total cm. kinetic energy (b) The IT -proton and K -neutron total cross sections are about the same in this energy range; the K" -proton cross section is roughly twice as large.(c) The contribution to the dispersion relation as evaluated by Matthews and Salam 5 is not negligible in the total energy range above 2m g as they assumed tentatively. Assuming from our results that o(K~) -o(K+) in the energy range 2 to 5 mj{ is 25 mb, we find a contribution of -0.5 in their units.The results of a new measurement of the 77"proton and 7r + -proton total cross sections and acknowledgments are given in an accompanying Letter. *