Mapping mountains where the Line’s sentries could not see presented particular challenges for Humboldt—and opportunities for the Empire. Here, again, Humboldt corroborated geological and ethnographic information. In <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0007842 https://www.geonames.org/515003">Orenburg</placeName>, he sourced topographical details from “a manuscript-map of the lands of the Small Horde” kept in an officer’s “rich Asiatic Collection.”<note xmlns="http://www.tei-c.org/ns/1.0" place="foot" xml:id="ftn46" n="46"> See editors’ note to <ref target="https://edition-humboldt.de/H0005449/95v">Humboldt RST I, 95v</ref>; <bibl corresp="https://edition-humboldt.de/DV9UD9GW">Humboldt 1844</bibl>, I, 276, nt.</note> According to Humboldt’s notes, the map corresponded to the geological and hypsometric investigations of <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0011769 http://d-nb.info/gnd/116691174">Gregor von Helmersen</persName> (1803–1885) and <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0011946 https://explore.gnd.network/gnd/116951079">Ernst Hofmann</persName> (1801–1871), also enrolled in <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0012872 http://d-nb.info/gnd/118666878">Cancrin</persName>’s mineralogical campaign. “Hofm[an] and H[elmersen] adopt my opinion of the prolongation of the <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0006673 https://www.geonames.org/1505865/">Ilmeny Mountains</placeName>,” Humboldt noted of the point at which the <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0009659 https://www.geonames.org/1488441">Urals</placeName> appeared to splinter into three chains around <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0015024 https://www.geonames.org/462444">Zlatoust</placeName>, south of <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0005599 https://www.geonames.org/1486209">Yekaterinburg</placeName>.<note xmlns="http://www.tei-c.org/ns/1.0" place="foot" xml:id="ftn47" n="47"> <ref target="https://edition-humboldt.de/H0005449/94v">Humboldt RST I, 94v</ref>–<ref target="https://edition-humboldt.de/H0005449/95v">95v</ref>. </note> As <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0017907 http://d-nb.info/gnd/1017902623 ">Tobias Kraft</persName> and <persName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0017958">Florian Schnee</persName> have indicated, a major focus of Humboldt’s notes from the <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0020292 https://www.geonames.org/466003">south Urals</placeName> was to delineate these splintered chains and the watersheds that fell into the “longitudinal valleys” between them.<note xmlns="http://www.tei-c.org/ns/1.0" place="foot" xml:id="ftn48" n="48"> <ref target="https://edition-humboldt.de/H0005449/82v">Humboldt RST I, 82v</ref>–<ref target="https://edition-humboldt.de/H0005449/84v">84v</ref>.</note> There appeared to him “no doubt” that the ridgelines of the Ilmeny Mountains were truly “a continuation of this same eastern chain, which after joining the central chain of <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0017489 https://www.geonames.org/556201">Irendik</placeName> and <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0011128 https://www.geonames.org/1517742">Guberlin</placeName> turn toward the isthmus between the <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0002514 https://www.geonames.org/1526250">Aral</placeName> and <placeName xmlns="http://www.tei-c.org/ns/1.0" ref="https://edition-humboldt.de/H0000384 https://www.geonames.org/630671">Caspian</placeName>.”<note xmlns="http://www.tei-c.org/ns/1.0" place="foot" xml:id="ftn49" n="49"> <ref target="https://edition-humboldt.de/H0005449/95v">Humboldt RST I, 95v</ref>.</note> The sweeping claim appeared to make light work of yet another fragmented mountain-system. In truth, though, a subtler rhetoric was required to make the Ural’s southern advance a fait accompli.