On the first working day of the last full week in January, I cup a hand to my good ear and listen.

Without fail, this is the day on which one can hear the first gurgle in the mail pipeline that for six weeks has been bringing in a steady stream of checks for Children's Hospital.

Our fund drive ends on Jan. 31, but by the last full week before that date the pipeline gurgles a signal that most of the money is in and the flow will soon end. The big question mark that remains is the size of the annual contribution from Mother Bell's children -- area employees of the Bell System.

While we wait for a phone call to tell us that Ma Bell is ready for the abacus and a tally sheet, let me report on the specifics of today's gurgle.

"The Third Shift in computer operations here at The Post rustled up $10 for the children," says the first letter, which is really an inter-office memo. Let the record show that the Third Shift is my shift -- the lobster shift, the one that bails me out when my video display terminal suffers a nervous breakdown at 5 a.m.

I don't know how to order my VDT to write C-cubed, so I'll have to spell it out. The letter said, "The men and women of the Strategic C-Cubed Division, Directorate of C-Cubed and Information, Hq U.S. Air Force, wish to share this $11.10 from their coffee fund with the children." C-Cubed is Air Force shorthand for Command, Control & Communications.

Let the record show that the Columbia Pike Thrift Shop's contribution is now $15.01 larger than previously reported. And the school reports published here are hereby updated to include $25 from the staff of the Westlawn Elementary School in Falls Church.

Col. David Marcus Lodge 211 of the Free Sons of Israel also sent me $25, as did the Baha'i Assembly of East Fairfax County, whose check was accompanied by a letter that said, in part, "Children's Hospital is an institution that can benefit all of us; in fact, over 20 years ago, it helped save the life of the author of this letter."

I'm glad to hear it, my friend. Ask yourself why it was God's will that you live and you'll have a pretty good blueprint of what He wants you to do with the years that have been given to you.

The Exchange Club of Washington D.C. sent me $37.50. "The Survivor Annuitants Service Section, Office of Personnel Management (formerly Civil Service Commission) had some funds remaining from a Christmas party," so the deficit at Children's Hospital has been reduced by $41.25. HELP (Help for Exceptional Little People) sent me $50. Two other $50 contributions arrived, both from American Legion units. One was from Cissel-Saxon Post 41 in Silver Spring and the other from College Park Post 217.

When the bills for its Christmas party were paid, the Office of Productivity and Technology of the Bureau of Labor Statistics had $52.06 left. How would you have solved such a problem? The statisticians did, too.

Food and Drug's Office of the Associate Commissioner for Regulatory Affairs sent $65 for the children. The English Department of the Model Secondary School for the Deaf heard the call for help from Children's Hospital with complete clarity and scrapped its traditional gift exchange to round up $105. My fingers are on my heart, ladies and gentlemen, and I'm sure we understand each other.

I don't know why anybody would want to shake a stick at the Library of Congress, but it has more nooks and crannies than you can shake a stick at, and they all seem to support The Hospital With the Built-In Deficit. The latest to check in is the Science Policy Research Division of the Congressional Research Service, where 11 staffers mustered a contribution of $120.

The second greatest invention of the modern era (the greatest is the remote control that turns off the sound on commercials) is corporate matching contributions. When employees of the Jensen Manufacturing Co. (Alexandria) collected $146 for Children's Hospital, their employer shelled out another $146 to bring the group gift to $292. And when eight ounces of checks from ADTECH (Advanced Technology, Inc.) employees added up to $578, the company "matched" the gift with $2,000. Do you think I am morally obligated to tell ADTECH it matched too much?

The abacus says these 17 groups have contributed $3,551.92, and that 40 unnamed individuals have added $1,118.50 to bring today's total to $4,670.42. Having begun the day with $153,512.54, the shoebox now holds $158,182.96. Ma Bell, where are you?