Fortifying a hot liquid, even water, with strong spirits is an instinct man has practiced since soon after he tamed fire. But it was natural for the lyrical Irish, in whose tradition whiskey runs almost as strongly as poetry, to devise the most satisfying of all toddies.

Those who anticipate raising a glass on or around St. Patrick's Day next Monday may appreciate some specific instructions. None were forthcoming from the contestant's in the Irish coffee contest, not because the contestants wouldn't be interviewed, but because exact measurements appeared to be a violation of the rules.

Here is how one impressionable visitor to Ireland remembers her introduction to the drink: "They made a sugar rim around the top of the glass, using demerara sugar. I guess they dipped the glass in hot water. Then they put in the whiskey, pouring it over some sugar in the bottom of the glass.The glass was almost filled with coffee and then cold heavy cream was poured on, over the back of a silver spoon held just above the surface. That way it stayed on top and didn't sink. As you sipped the cream would cool the coffee. Whipped cream was considered very non-U."

In this country, where the cream is as thin as watered-down whiskey, whipped cream is U enough. (Furthermore, if you want to skip the coffee, there is a delicious product called Bailey's Irish Cream that combines cream and Irish whiskey.) Irish coffee lovers do have standards, however. They draw the line at artifical toppings from a can and will frown at the suggestion of instant coffee. Irish whiskey is essential. It is made from a mash that included malted barley and other grains. Unlike the grains used in Scotch whiskey, the malt is not smoked cured. The whiskey that emerges from the still will be aged from four to eight years and is very smooth.

To use it in the "classic" recipe developed at the Buena Vista Cafe, as reproduced in "Grossman's Guide to Wines, Beer & Spirits" IRISH COFFEE (1 serving) 1 teaspoon sugar 1 1/2 ounce Irish whiskey 5 ounces very hot, strong black coffee Whipped cream

Rinse an 8-ounce stemmed goblet with very hot water. Place the sugar in the glass and pour in the Irish whiskey and coffee. Stir to dissolve sugar and top with whipped cream.