Three areas of study, relating to volume
From "Tape reading and market tactics" - Humphrey B. Neill
General Principles.
1st. Increasing volume "during" an advance,with intervening pauses or set backs occurring on light volume. This is indicative of the underlying demand's being greater than the supply, and favors a resumption of the advance.
2nd. Increased volume at the "top" of a rally,or of an advance, lasting for some time, with no appreciable gain in prices - an active churning of stock transactions without progress. This is indicative of a turning point.
3rd. A "tired" or struggling, advance, when stocks creep upward on light volume and "die" at the top. This indicates a lack of demand ( few buying - orders) ;and, whereas selling - orders likewise are light, this action frequently marks a "rounding - over" turn, which may be followed by increased volume on the down side ( when the sellers see that they cannot hope for much higher prices at the time). These struggling trends are subject to sudden reversals, particularly when they have endured for several days.
These types of action are present, but reversed in sequence in declining markets.