1. Data: The construction shows a clear downward trend over time. It was most frequent in the early-to-mid 19th century (1820s-1850s), with a peak in the 1830s. From there, it began a steady decline, with particularly sharp drops between 1910-1940. The frequency continued to decrease through the late 20th and early 21st centuries, reaching its lowest point in the 2010s, roughly one-tenth of its peak frequency.

2. Possible explanation: The pattern suggests a clear case of grammatical obsolescence, where a more complex formal construction gradually falls out of regular use. The construction "so ADJ as to V" is syntactically elaborate, requiring multiple elements (so + adjective + as + infinitive) to express degree and consequence. The steady, consistent decline rather than sudden drops indicates this is a systematic change in English grammar rather than a temporary stylistic shift. The steeper decline during 1910-1940 might represent a critical period when the construction began to be perceived as notably formal or archaic, accelerating its replacement by simpler alternatives.

3. Competing constructions: Several simpler alternatives likely replaced this construction: - "Too ADJ to V" (e.g., "too small to see" instead of "so small as to be invisible") - "ADJ enough to V" (e.g., "fortunate enough to find" instead of "so fortunate as to find") - Simple intensifier + adjective (e.g., "very small" or "really good") - Direct causative constructions (e.g., "making it impossible" instead of "so difficult as to be impossible") These alternatives achieve the same semantic function with less syntactic complexity, following the general linguistic principle of economy.