The true first issue of Halley’ comet. Bibliographically, this first issue is very interesting. The Phil Trans of this period were issued initially in separate bimonthly parts which were sent to the Fellows of the Royal Society. These separate issues were eventually bound up as volumes with supplied title page and index, either by the Fellows, or if remaining undistributed stock had rather a limited sale or were used to gift or to exchange with other scientific luminaries of the times here and overseas. Halley had been working on the mathematics of comet rotations for some time, and eventually published in 1705 three different versions of his argument: the first that which we have here, in Philosophical Transactions dated March 1705; the second also in Latin in June 1705 as a separate slightly shorter pamphlet with Clarendon Press, and the third, in English, translated by Senex. The Norman catalogue mistakenly suggests that the Clarendon Press pamphlet is the earlier in precedence, but this is both contradicted by the date (the Phil Trans version is dated three months earlier, March 1705, than the pamphlet which is dated June 1705), and also by the minute analysis of Rigaud, the early Oxford historian of science, in which he points out that the separate Clarendon pamphlet incorporates authorial changes which were clearly initially rather compressed into the Phil Trans version, as well as marking a softening of Halley s rather confident earlier claim of his correctness in predicting the comet's (now known as Halley s comet) return (see Rigaud, Some Account of Halley s Astronomiae Cometicae Synopsis which contains his investigations of the orbits of comets, Oxford 1835). Halley’s analysis is regarded as being one of the most important astronomical discoveries, and indeed one of the most important scientific discoveries of all time. The Clarendon pamphlet sold for $144,500 at the Norman sale in 1998: we can trace no examples of the Phil Trans version on the market.