Giving Red-Flannel Hash Its Culinary Due

IN the good old days, one could climb two flights of steep stairs to Thompson's Spa on Boston's Newspaper Row and lunch with some of the world's richest men on red-flannel hash for 35 cents. The hash, it was emphasized, came with a single poached egg, or as it was properly identified on the menu card tacked to the wall, a ''dropped'' egg. The paean I wrote on this subject prompted a little over one wheelbarrow of reader mail, and I now quote from one letter:

''On the S.S. Bremen in 1966, the breakfast menu offered Sailors' Labskhaus. When set before me it was corned beef hash with a poached egg smiling up at me. Robert W. Hill''

Mr. Hill asks if this might be a relic of Maine lumber camps and several other pertinent questions, and then departs to attend his philanthropies while I confer with the reference librarians and compose the answers.

First, consider the Mayflower, the small sailing vessel that brought the Pilgrims, their tall clocks, and their Governor Winthrop desks to America in 1620. Had she not chartered for this historical voyage, as a member of the British North Atlantic fishing fleet, she would, instead, have gone to Spain to load salt, which she would have next delivered to the fisheries on Monhegan Island for 27d a bu. Very good tariff. Salt was essential to corned hake, etc.

This was a white salt, good quality for the times, and while it came from Spanish pits it became Liverpool salt once in an English vessel's hold. It is a coarse-grained salt, also used for salting loose hay in a mow, making pickles, and corning the brisket for a New England boiled dinner.

There exist in many old-time Maine cookbooks certain recipes for a ''lobscouse.'' And in early German cookbooks you will find equal attention to a ''labskhaus.'' I see no reason to argue with any student who relates this to a boiled dinner, frequently called corned beef and cabbage, and in context with a George McManus comic strip about a century ago, a Jiggs Dinner. In the German cookbooks, labskhaus is said to be a North German delicacy, possibly to forestall lawsuits by Bavarians. Let us be neutral. We are perhaps halfway to the poached egg.

A piece of lesser beef is the foundation. It will be lightly corned in a brine that will float a potato and sometimes is also ''freshened'' just before cooking. The German recipes say ''pickled'' meat. Simmer somewhat in the family ''scousepot'' (a Dutch oven) and then add vegetables. The list: cabbage, onion, potato, carrot, turnip, and beets, but do the beets in a separate pot and serve on the side.

Now, this piece of cheaper beef wants to be corned with pickling, or Liverpool salt, and never, never with any substitute that will make the meat red. I have spoken.

So now we come to what reader Hill is talking about, which is or are the leftovers. Give the family at least a full day to meditate on the beauties of a boiled dinner and then fetch on the red-flannel hash. Red flannel? It was the fabric identified with long-handled winter underwear, snug and cozy, the only thing for a long, hard winter, and meant to stick to the ribs and not digest on you right away. You don't split wood all day on nothing but snacks and thin cookies.

The red color of the hash comes from the beets, which are now meat-grindered along with the remaining corned beef and vegetables and pattied into round cakes for pan-frying.

Frau Hanni Hendel, who permitted me to look in her German cookbook for labskhaus, pointed out that ''Serve with eggs'' may or may not mean what we call a poached egg or a dropped egg. She couldn't remember. I seemed to detect in Hanni's attitude a certain dubious regard for a labskhaus, as if 'twere a peat-farmer's sorry substitute for the high cuisine.

I detected this again when I asked Frau Barbara Wolter if she made a good labskhaus and she said, ''Only by request.'' And I think it is possible that in the old lumber-camp days in the Maine woods corned beef was considered ''living short.'' Fresh meat was just outside the door, running wild.

For an opposite reason, I doubt if boiled dinners were seen too often by sailors; it was hard to come by garden vegetables on long voyages. Fact is, the Nobleboro and Damariscotta Ladies' Aid Cookbook gives a meager lobscouse for a seafaring readership: ''Take cheap beef and simmer three hours with an onion.'' That's it! Nancy, our neighbor, says, ''Sounds slim to me.''

And the leftovers would be slimmer on red-flannel hash day. Thompson's Spa on Newspaper Row, with the whole building that housed it, is memory only. The kitchens were below ground, and food was lifted to the second-floor dining room on dumbwaiters. Instead of tables, the place had semi-oval counters with a waitress inside for each dozen diners.

Mr. Thompson himself was said to recruit his waitresses in the Maritime Provinces. Many a farm girl from P.E.I. and New Brunswick thus came to wed a Boston financier or a journalist of note, as some six newspapers and the State Street financial institutions provided most of the Thompson Spa customers, who always knew their pretty waitresses by first name.

Maybe Mr. Hill will favor us with another letter about labskhaus and include a few observations about the Frauleins in the dining saloon aboard the S.S. Bremen in 1966.

Please.