A letter that arrived at the end of last week said, "Please don't forget to remind us how to avoid writing '1978' on the datelines of our checks."

Thanks for reminding me that I'm supposed to remind you. You are hereby reminded that the easy way to avoid writing "1978" on this year's checks is to get out your current pad of blank checks right now and fill in "1979" on the dateline of each. By the time you use up one pad of checks, you will be accustomed to writing "1979."

We begin the final month of this year's campaign for Children's Hospital with $71,932.97 in the shoebox. On Jan 1, 1978, we had $79,429,03. At this rate, we could be $25,000 short by the time our campaign ends on Jan. 31, and that would be most unfortunate.

Inflation has driven up hospital operating costs as inexorably as it has boosted the totals on supermarket cash register tapes. The cost of providing medical help for poor children is more this year, not less.

If we want Children's Hospital to continue to serve the poor as well as the rich (or the insured), we must provide it with the money it needs to pay for such services.

I hope District Liners will begin the new year with renewed determination to help the hospital continue its century-old tradition of never truning away a sick child for lack of money.

Today I can report to you that the Commissioned Officers Association of the U.S. Public Health Service has sent me a check for $10. DARCOM's DRCPI added $20, and as any Soviet spy can tell you, DARCOM is Army Materiel's Development and Readiness Command, and DRCPI is DARCOM's Product Improvement Office.

"The First Road South (Arlington) Carolers", all under 8 years of age except for a few daddies and mommies, earned $25 for the hospital. Another $25 came from the Office of the Special Representative for Trade Negotiations. A third $25 check was simply marked, "From CCC Poel."

A $30 check was identified as the contribution of "The 11th and 12th Street Southeast Club," and another $30 check was raised by a caroling group that included "one niece, one nephew, one neighborhood child, two adults and two dogs."

Three of today's checks were for $50 each. One was from employees of Fine Print, Inc., one from the Eckington Neighborhood Club, and one from the Senate Committee on Veterans' Affairs. Employees at W. Bell & Co. headquarters raised $70.45.

A delightfully humorous "legal document" accompanied a check for $100 from the Legal Department at the National Association of Broadcasters. If space permitted me to reproduce the document here, I think you'd agree that the lawyer who wrote it should be writing comedy programs.

From the University of Maryland came $110 raised at bake sales and white elephant sales by PALS, which even a Soviet spy might not know is an acronym for Physics & Astronomy Ladies Society. "Employees of our law firm" sent me $116.85 with a Silver Spring address as the only clue to the firm's identity. Alley Kats Bowling League in McLean rolled $120 down my alley. And those tough guys in the Metropolitan Police Department's Special Operations Division -- the unit that must at all times be prepared to respond five minutes ago -- again turned out to be soft touches where kids are involved. They chipped in $121.

Customers and employees of Peoples Drug Store 288 (on Bel Pre Road) decorated a money tree with 154 beautiful green dollars. At Beltway Glass in College Park, this year's kitty grew into a healthy $180 cat.

The Resource Monitoring Branch of the Pentagon's Command and Control Technical Center (which for some reason is known as FORSTAT) rounded up $188.42 -- an increase of more than 50 percent over its contribution to last year's campaign. And employees of Val-Pak of Maryland also demonstrated a keen awareness of how to cope with inflat2on by sending me a $200 boost for the shoebox.

As usual, employees of the Environmental Protection Agency's Office of Water Program Operations exchanged no intra-office cards and thereby saved $223. And top honors for the day went to the Veterans Administration's Office of Construction, which used the no-cards idea to raise $431.25.

My count shows 22 groups and a total of $2,329.97. Also 58 checks from anonymous individuals who gave the children $1,354.15 and brought today's total to $3,984.12. The shoebox now holds $75,917.09. Help!