THE RHONE, one of the world's great wine rivers, traverses a great diversity in climate and soils, and creates a haven for wine grapes along much of its length in Switzerland and France. The region associated by name with the river is the so-called Cotes du Rhone region of southern France, which stretches roughly from Lyon in the north to Avignon in the south.

The vineyards fall distinctly into northern and southern regions separated by a 60-kilometer gap of no recognized cultivation. Wines from the two locales offer dramatically different styles, and each area requires individual treatment. The south was examined in last Thursday's Food Section. Today, the wines of the north.

Vineyards in the north are adjacent to the river, primarily on certain preferred southerly facing slopes. The vines themselves perch, sometimes precariously, on steeply terraced cliffs of crumbling granite. The noble Syrah (no relation to the Petit Sirah of California) predominates. Red wine appelations in the north (roughly in order of their general quality) include Cote Rotie, Hermitage, Cornas, St. Joseph and Crozes Hermitage. The wines are customarily vinified for extended aging and, when young, tend to be hot, green, hard and unbalanced. With sufficient bottle aging they become expansive, round, supple and velvety.

Probably the best of all northern Rhone vineyards is the "roasted hill" of Cote Rotie. Situated south of Vienne over a providential bend in the river, these diminutive, steep Syrah vineyards have been famous since the days of Rome. They are terrace by old stone retaining walls and are worked completely by hand; nevertheless, the soil migrates downward and must be periodically replaced. The roughly 10,000 case production -- fragmented among a number of producers -- is typically Burgundian and boutique even by California standards.

The better wines, after proper (considerable) aging, are said to be the most complex and rewarding of all Rhones, but also the most subtle (a relative term in this case). Like Chianti, the wine is blended with a small percentage (10 to 20 percent) of white wine -- the classic Viognier for which nearby Chateau Grillet is famous - to buffer the intensity and add finesse. The classic smell is one of earth, truffles, tea leaves or chocolate. The best have a rich, earthy, "roasted" flavor, alcoholic character, and a long, delicate nutty or woody finish. When young they assault and overstimulate the palate with immense tannin, biting acidity and heady, unbalanced alcohol.

About 50 kilometers south of Cote Rotie, on another favorable bend in the river, the famous granite hill of Hermitage towers over the town of Tain-l'Hermitage. Names most probably for a legendary knight who returned from the Crusades to become a hermit, these red vineyards were rated in the last century, along with Lafite and Romanee-Conti, as the best in the world. Indeed, it is said that Hermitage once was used as a blending wine to fortify Lafite. As in Cote Rotie, the vineyards are among the oldest in France and have many owners. The stone terraced plots of meager lime and granite soil are quite small and produce only about 25,000 cases per year.

Hermitage is rightly considered the "manliest" of all wines with deep colored, rich, almost port-like quality. As in Cote Rotie, the intense but harsh Syrah character is frequently blended with a small percentage of Viognier for roundness. The style is generally fuller than Cote Rotie; the fruit is wood aged away leaving a pungent vinosity in the young wine which must be very slowly matured out.

As with Cote Rotie, the young wines are virtually undrinkable, and the longevity is proverbial; these are some of the longest lived of all wines. Greater than a 100 years is possible, and 20 years is essential for the great wines. With maturity achieved, the color becomes onion skin; the character generous, heady, expansive and velvety; and the scent and flavor a blend of wood and carmelized fruit. Unfortunately, they are rarely kept long enough to acheive this style. As might be expected, not all producers create such high quality wines; nor are all vintages appropriate for their production.

Neighboring vineyards are entitled to the names Crozes Hermitage; this is perhaps a poor choice because these vines are of completely different style and of significantly lower quality (and price as well). They are, in effect, the generic of the north. Across the river to the west lie the vineyards of Cornas and St. Joseph. The former are high quality, sturdy wines (somewhat similar to Hermitage with earthy flavors) and age well; the latter are lighter, more delicate wines with perhaps more perfume but less body, and are closer to Crozes Hermitage in style.

In a recent tasting, the wines favored for current consumption (but with considerable aging potential remaining) were the 1973 Cote Rotie "Le Jumelles," P. Jaboulet ($9 at MacArthur) and the 1970 Cote Rotie, Dervieux-Thaize ($6 at ShopRite -- a rare bargain.)

Drinking well now in lighter style with limited aging potential was the 1973 Hermitage-Rochefine, Jaboulet-Vercherre ($6 at Woodley). Wines still young and rough but felt to have good future potential were the 1971 Hermitage "La Chapelle," P. Jaboulet ($10 at Woodley), the 1976 Hermitage, Chapoutier ($7 at Woodley) and the immense 1970 Cornas, P. Jaboulet ($10 at A&A). The latter is a classic monster: unbalanced and unpalatable now, but with grand dimensions of fruit oak, acid, and tannin. In another 10 years this could be a magnificent bottle.

The label most in evidence on local shelves is that of Paul Jaboulet, a respected producer with wide holdings who exports wines from all appelations. Each of his wines was found at or near the top of its respective category. The wines of Crozes Hermitage were uniformly disappointing and fell at the very bottom of the rankings.

Vintages of the past 20 years generally considered very good or better throughout the north are 1961, '64, '66, '67, '69, '70, '71, and '76; '72 and '73 produced some very good wines; '74, '75, and '77 are below average and best avoided; the '78s appear to have a bright future. The '73s are generally drinking well now; the '70s, '71s and '72s still have a way to go; the '76s are several years from a difinitive evaluation. Decanting prior to serving is strongly recommended: the younger the wine, the longer the lead time.

The better northern wines are more or less unique in an "old world" sort of way. They must be classed as "connoisseur's wines" are characteristically far from being ready to drink straight off the shelf. A great wine from Cote Rotie, Hermitage, or Cornas demands long cellar aging -- not just five years, but more like 10 or 20 at a minimum. These are not wines for the average consumer.

Recently somewhat undervalued, they are once again exacting heady prices because of their proximity to badly inflated Burgundy. Shopping with great care, one can find some superior wine for a price. High cost is no guarantee of a good wine, but a price under $5 almost certainly guarantees a disappointing one.