Who this entry is for — Charting's most basic tools, explained by the model: why price "respects" certain straight lines, and why their break really does announce a reversal.
Source: J. M. Hurst, The Profit Magic of Stock Transaction Timing, Prentice-Hall, 1970 — Chapter 3, Why Trend Lines and Channels Form — and Repeat (pp. 52–56).
Prerequisites
Five principles of the cyclic model (summation) and the Curvilinear envelope.
The minimal recipe: A + B = C
In plain words — Take a single cycle and a rising line. Add them. You get a price bouncing between two parallel straight lines: a channel. The chartist draws it; the model explains it.
Hurst extracts from the model "the simplest possible set of elements": any one cyclic component (A), the sum of all longer components reduced by assumption to a straight line (B), and their point-by-point sum (C). The result already contains an uptrend line and a rising channel:
Trend lines, Hurst observes, are often described "in awe-filled tones", because prices seem to bounce off them as if they were real constraints. But there is no magic here at all: it is the natural result of the existence of "X" cyclicality.
True channels are curved
In plain words — The chartist's straight line is a straightened stretch of the envelope, which actually curves. When the long cycle turns, the envelope turns with it — and price "breaks" the straight line.
Overlaying the constant-width envelope on the same simulation (the book's Fig. III-5), Hurst shows two things:
- the envelope is a mandatory outgrowth of the model — and when fluctuations do not fill it, that is a warning: a magnitude-duration fluctuation is forming;
- the chartist's trend lines and channels are straightened segments of the envelope's bounds, which are actually curvilinear.
Hence the true meaning of the break. When a cycle longer than the one contained in the channel begins to turn, the curved channel turns with it and price quickly crosses the chartist's straight lines. His empirical rule ("break = significant reversal") rests on two facts of the model:
- the effect is caused by a long cycle → it will be quite a while before the previous trend resumes;
- a long cycle carries large magnitude (proportionality) → the reversal move is apt to be large.
Example — The chartist says: "uptrend line broken after three touches — expect a significant reversal." The model translates: "the cycle that held those lows has been overruled by a longer one that turned — and the longer one is also the larger."
Which trend line counts?
Warning — At any instant, on the same stock, valid trend lines exist both up and down: one per cyclic component. Charting cannot say which to trust; the model can — all of them, each at its own scale, with importance set by the magnitude-duration relationship. That is the "reference time" problem Chapter 3 solves.
Summary card
| Chartist's element | Cyclic translation |
|---|---|
| Uptrend line | Line through the lows of one component above the sum of longer cycles |
| Channel | Straightened segment of the curvilinear envelope |
| Break | A longer cycle has turned |
| "Trends tend to persist" | True until the longer cycle rolls over |
| Size of the reversal | Proportional to the duration of the cycle that turned |
Links
- Chart pattern verification — Chapter 3's framework
- Head and shoulders — the neckline is a second trend line
- Curvilinear envelope — the "true" channel
- Hurst tradition — chapter index