[OAB 42], and [OAB 36] Dr. Gentry (see Parentless polonium halos, above) also measured the amounts of helium and lead (both products of radioactive decary) in zircon crystals from a single granite formation. The present temperature at each depth sampled was recorded. The depths ranged from the surface to 4310 meters, while the temperatures ranged from 20 to 313 degrees centigrade. Using standard methods to determine the amount of lead produced by radioactive decay in the samples, Gentry found that practically all of the expected lead was present in the samples, even though the lead would be expected to have diffused away from the samples due to the high temperatures (R.V. Gentry et al, Science, v.216, pp.296-298 (16 April 1982)). In his book Creation's Tiny Mystery, Gentry proposes an age limit of 300,000 years based on his lead findings. Similarly, judging the amount of helium produced from the amount of lead present, he found a significant amount of helium (from 17% to 58% of his calculated limit) in samples down to 2900 meters of depth. Again he argued that the helium should have diffused away due to the high temperatures if the sample were really hundreds of millions of years old. On the other hand, and this may be of great importance, Gentry reported that practically all of the helium had diffused away in the samples from deeper than 2900 meters (R.V. Gentry et al, Geophysical Research Letters, v.9, no.10, pp.1129-1130 (1982)). The likely explanation for Gentry's findings seems to be that the formation from which he drew his samples has only recently been subjected to temperatures high enough to cause diffusion. If so, the lack of diffusion then would not date the rock formation itself, but rather the onset of high temperatures. This is especially indicated by the complete diffusion of helium in his deeper samples, since helium diffuses more easily than lead, and the deeper parts of the formation would be expected to experience higher temperatures earlier than the shallower parts. In fact, Gentry acknowledges in the above-cited Science article that temperatures in the formation are indeed thought to be rising. Need confirmed rebuttal from knowledgable source. These claims are not present in the Defender's Bible, indicating that they have been abandoned by ICR as weak.¹