"These are the cars poultry is shipped in," explained Uncle Robert. "Perhaps they have been to Chicago with chickens for the market, and are on the way back to the place they came from for more." "How many of these big yellow cars there are!" said Susie. "They all have re-frig-re-frig--" "Refrigerator," prompted Uncle Robert. "Oh, I know what a refrigerator is," said Susie. "It's an ice box. Are these cars ice boxes, uncle?" "Yes; the great packing houses at the stock yards in Chicago ship beef all over the country in them. The fruit from California comes in refrigerator cars, too." "There's the train!" cried Susie, "and here comes Mr. Jenkins with the mail." The train came rushing on. Susie thought it was not going to stop. But suddenly it slowed up. The conductor leaped upon the platform. The train stood still. Heads were thrust out of the windows. A few passengers alighted. Brakemen ran along the platform. "All aboard!" shouted the conductor, waving his hand to the engineer, who was leaning out of the cab window watching for the signal. "Ding-dong, ding-dong, puff, puff, toot, toot," and the train was off. "Now we'll go and see if there is any mail for us," said Uncle Robert. "Then we'll go to the tinsmith's." [Illustration: Rain-gauge.] The rain-gauge was just finished. So Susie waited in the shop while Uncle Robert went to the stable for Nell, who pricked up her ears when she saw him. She was beginning to think she had been forgotten. It was late in the afternoon when they reached home. Mrs. Leonard and the boys were looking for them when they drove in at the gate. It took some time to choose just the right place for the rain-gauge, but at last they decided upon a little rise of ground that lay between the house and the orchard. There was first the funnel-shaped receiver, one and one-half inches deep and eight inches in diameter. Below this was a tube two and five-tenths inches in diameter and twenty inches long. At the top of this tube, close to the receiver, there was a small hole. "What is that hole for?" asked Donald. "So if it rains more than enough to fill this tube," explained Susie, who knew all about it, "it can run out of the hole." "Then it will be lost," said Donald. "No," replied Uncle Robert, "it is to be set inside of this cylinder, which is twenty-three and one-half inches long, but only six inches in diameter, and so is smaller than the top of the receiver. "The water that runs from that hole falls into this. By measuring it in the small tube, and adding it to what the tube held before, we can know how much there is in all. One inch in the tube would be one-tenth of an inch in the receiver." "Then twenty inches, or the tube full, would be two inches in the receiver," said Frank. "Yes," said his uncle; "but how shall we make this stand up?" "We might pile stones around it," suggested Donald. "That will be a good way," said Uncle Robert.