Washington Gas Light Co., the natural gas utility serving most of the Washington area, said it lost $4.8 million in the third quarter ended June 30, slightly more than the $4.5 million the company lost in the same quarter a year ago. Revenue fell 13 percent in the quarter, to $111.7 million from $128.9 million.

A spokeswoman for the company said Washington Gas typically loses money in the April-to-June quarter, when warm weather sharply reduces natural gas demand. Somewhat warmer than usual weather heightened the loss, she said.

In the first nine months of its fiscal year, Washington Gas earned $57.8 million ($2.97 a share), a 3 percent increase from $56.3 million ($3) a year ago, when the company had fewer shares outstanding. Revenue fell 5 percent, to $635.6 million from $672 million a year ago.

Norfolk Southern Corp. said its second-quarter earnings fell 10.2 percent from a year earlier, when the company had a one-time $13.6 million gain.

The railroad and transportation company earned $155.9 million (95 cents), down from $173.7 million (99 cents) in the 1989 second quarter. Revenue totaled $1.18 billion, up from $1.17 billion in the comparable 1989 period.

Norfolk Southern attributed the decline in part to the $13.6 million after-tax gain that inflated its 1989 second-quarter earnings. The gain came from the sale of part of its trailer train holdings.

For the first half, Norfolk Southern earned $296.1 million ($1.79), down 3.7 percent from $307.5 million ($1.74) in the first six months of 1989. First-half revenue totaled $2.32 billion, up from $2.29 billion.