As an example flow (since it took a minute to figure out): we can start at https://en.wikisource.org/wiki/1911_Encyclopædia_Britannica then click to navigate/browse volume > section > topic to get to a text page, then click Source tab, then click a Page Number (maybe hunt around for the correct page number), and see the parallel view, text + image. With previous and next page buttons available, retaining the parallel text + image view.
1. Go to https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britan...
2. Click button "Search the 1911 Encyclopædia Britannica". This currently goes to the page at https://en.wikisource.org/wiki/Special:Search?search=&prefix...
3. Enter the search term and click Search. (There is auto-suggest for some topics, but Search button seems to give more complete results.)
4. Get to the text page of interest, such as https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britan...
5. Notice the left margin contains hyperlinks like [105] whwere 105 is the page number nd links directl;y to the side-by side view of page 105. Click the [105] link on the left (for example), to get to https://en.wikisource.org/wiki/Page%3AEB1911_-_Volume_02.djv... which shows the text-and-image side by side (for that page).
This flow avoids the hunting-for-the-right page step, by using the direct links.
Thanks for the suggestion.
You can already do that on Wikisource. For example, here's p. 658 from the entry on "Molecule":
https://en.wikisource.org/wiki/Page:EB1911_-_Volume_18.djvu/...
Also OP: I noticed some fidelity issues in your version (at https://britannica11.org/article/18-0684-s2/molecule). For example parts of the math formula under the line that ends with "the molecules of other kinds" ([1]) are missing (compare [2]). Also, in your version fn. 1 of this article is attached to "as they have always done" ([3]) but it should actually be attached to "Atom" on p. 654 ([4]):
[1] https://britannica11.org/article/18-0684-s2/molecule#:~:text...
[2] https://en.wikisource.org/wiki/Page:EB1911_-_Volume_18.djvu/...
[3] https://britannica11.org/article/18-0684-s2/molecule#:~:text...
[4] https://en.wikisource.org/wiki/Page:EB1911_-_Volume_18.djvu/...