Data: I looked for similar data on sentence lengths in german, and the first result I found covering a similar timeframe was wikipedia referencing Kurt Möslein: Einige Entwicklungstendenzen in der Syntax der wissenschaftlich-technischen Literatur seit dem Ende des 18. Jahrhunderts. (1974), which does not find the same trend:
Year
wps
1770
24,50
1800
25,54
1850
32,00
1900
23,58
1920
22,72
1940
19,60
1960
19,90
This data on scientific writing starts lower than any of your english examples from that time, and increases initially, but arrives in the same place (insofar as wps are comparably across languages, which I think is fine for english and german).
Data: I looked for similar data on sentence lengths in german, and the first result I found covering a similar timeframe was wikipedia referencing Kurt Möslein: Einige Entwicklungstendenzen in der Syntax der wissenschaftlich-technischen Literatur seit dem Ende des 18. Jahrhunderts. (1974), which does not find the same trend:
This data on scientific writing starts lower than any of your english examples from that time, and increases initially, but arrives in the same place (insofar as wps are comparably across languages, which I think is fine for english and german).