a pyrrhic followed by a spondee, and like a 4-syllable "ascending foot" that functions as a unit. Rhythmi-metrical scansion The two main approaches to scansion result in a conundrum: metrical scansion necessarily ignores significant differences in stress, the very signal that meter orders; yet rhythmic scansion obscures meter and tends to be overly subjective. Jespersen provided the components of a solution to this problem by both (1) marking multiple levels of syllable stress, and (2) defining the meter of iambic pentameter as a series of 10 syllabic positions, differentiated by rising or falling levels of stress. Numeric stress levels are as described above, and "a" and "B" represent weak and strong positions in the line; alternatively (3) "a/b\a/b..." represents relatively stressed or unstressed positions, where the slash and backslash simply indicate stress levels increasing or decreasing. (1) 2 4 1 4 3 4 3 4 1 4 When Ajax strives, some rock's vast weight to throw, (2) a B a B a B a B a B (1) 1 4 3 4 1 2 1 4 3 4 The line too labours, and the words move slow; (3) a /b \ a / b\a / b \ a /b \ a / b However, Jespersen did not fully integrate his notation (even to the level implied by the scansions above). It remained for the Russian linguistic-statistical school to systematize it; in their 1968 study of Russian verse, A. N. Kolmogorov and A. V. Prokhorov used a system which made both stress and ictus explicit simultaneously. This basic approach has subsequently been used to scan English verse by Marina Tarlinskaja, Derek Attridge, and Peter L. Groves, though their systems differ in detail and purpose. In addition to making rhythm and meter distinct, all three prosodists provide explicit rules for assigning stress levels so that, as far as possible, this becomes an objective process driven by lexicon and syntax, rather than depending upon the "ear" of the scanner. Their works must be consulted for details, but a simplified version of Groves's rules can provide a first approximation: Primary stress: the primarily stressed syllable in content words (nouns, verbs, adjectives, and adverbs). Secondary stress: the secondarily stressed syllables of polysyllabic content words; the most strongly stressed syllable in polysyllabic function words (auxiliary verbs, conjunctions, pronouns, prepositions); subsidiary stress in compound words. Unstressed: unstressed syllables of polysyllabic words; monosyllabic function words. For comparative purposes,