Many introductory texts dedicated to Hegel’s Jena system (or systems) shy away from discussing his philosophy of nature, including the ultimate decision not to translate texts related to it into English. Both Leo Rauch book (Hegel and the Human Spirit) and H.S. Harris et al. book (The Jena System, 1804-05: Logic and Metaphysics)
on Jena do not include any texts on philosophy of nature. Both clearly state that Hegel’s system included the discussion of nature (Nature) as its essential component.
The most common explanation is that Hegel’s philosophy of nature – either early or mature – is obscure and irrelevant for contemporary readers. Here is how Rauch justifies taking out the section on philosophy of Spirit and leaving out the one on philosophy of Nature for his book:
The Jena lectures of 1805-6 comprise an internal duality themselves, since there is a section on the philosophy of Nature and another on the philosophy of Spirit. The former includes topics such as mechanics, chemistry, and physics, which are discussed in a way that is rather abstruse and the entire section is by now well out-of-date. The section on the philosophy of Spirit, on the other hand, has much to say to us today, and offers discussions on the topics of intellect, will, recognition, alienation, property, law, crime and punishment, social classes, and the theory of culture. 
So Hegel’s discussion of Spirit is relevant while his discussion of Nature is not – all of that after everyone constantly stresses that it is the system that matters for Hegel, not its individual parts. Rauch himself opens his Introduction with a rather sensible summary of the problem: “The Jena lectures are an attempt at presenting a comprehensive world-system. Any such system must include (and reconcile) two seemingly opposed aspects: the world of physical nature and the world of mind.” 
So if we are to present a comprehensive “world-system,” then we must present all of its aspects – any one-sidedness or partiality (here meaning the state of being partial, being only a part) is falsehood. So is it fair to exclude Hegel’s philosophy of nature from discussions and pretend that simply taking his logic would do?
P.S. Rauch notes in his Preface that “(As for the 1805-6 lectures on the philosophy of Nature, no doubt someone will be coming forward with a translation of them before long.)). This is 30 years ago in 1983. I don’t think such translation exists yet, does it?