Halliday & Matthiessen (2014: 618-9):
Manner conjunctives create cohesion (i) by comparison, (ii) by reference to means. Comparison may be (a) positive (‘is like’), or (b) negative (‘is unlike’).
(i) comparison:||| One area [[ that holds considerable promise for RC involvement]] is Information Operations. ||| By exploiting the technical skills [[ that many reservists use on a daily basis in their civilian jobs]] , || the military can take advantage of industry’s latest techniques [[ for protecting information systems]]. ||| Similarly, [[ defending our homeland from terrorism || and responding to chemical attack]] are natural roles for our Guard and Reserve forces. ||| [positive]
(ii) means:||| Chert originates in several ways. ||| Some may precipitate directly from sea water in areas [[ where volcanism releases abundant silica]] . ||| Most comes from the accumulation of silica shells of organisms. ||| These silica remains come from diatoms, radiolaria, and sponge spicules, || and are composed of opal. ||| Opal is easily recrystallised to form chert. ||| Thus much chert is recrystallised, || making the origin difficult to discern. |||
Expressions of means are however not often conjunctive; those that are are usually also comparative, e.g. in the same manner, otherwise.