In the article by Bigelow and Esty,1 the term "thermal death point in relation to time" was used to designate the time necessary to destroy bacterial spores at a specified temperature, the kind of medium and its hydrogen-ion concentration also being given. In this article the term "thermal death time" is used to express the same idea. In fig. 1 of the article mentioned is shown a series of curves on coordinate paper representing the thermal death times of the spores of various thermophilic bacteria at intervals of 5 C. On the opposite page are given the detailed data from which the curves were constructed. It is noted in the same article that since the curves on fig. 1 are approximately parallel, it is necessary to determine only the time required to destroy a given number of spores of an organism of this class at a given temperature in order to construct the entire curve. The writer has since plotted the same curves on semilog paper, and the resulting straight line curves show in a much more striking manner than do the curves on coordinate paper the relations to each other of the thermal death times at different temperatures. In table 1 of the article mentioned are shown the longest time each organism survived and the shortest time in which all spores were killed at each of several temperatures. In chart 1 of the present article the last positive and first negative results of 6 organisms taken from the table referred to are entered on semilog paper, and the points of observation for each organism at different temperatures are connected by a straight line. Numbering the curves from left to right, the time which the organisms survived is indicated by a plus sign on the first, third and fifth curves and the shortest time required to kill them by a circle. On the second, fourth and sixth curves these times are represented, respectively, by a cross and a dot. The 6 curves represent the results from 6 typical organisms taken from the table referred to. In this way it is made clear to which curve the various observation points belong. The curves are