Aa illui-tration of popular ignorance as to ventilatioD is furnished by the Sanitary Kngineer, and is as follows : A gentleman wliile atlending church one evening found that his feet were iey cold, so tliat he had to raise thein froin off the floor. Calling the attention of the eexton to this fact, the latter said, with some perplezity : "Yes, we have a good njany complaint.s of cold feet from otliere ; but 1 doa't understand the reason why wc can't keep the church warm ; we simly have fires enough." So saying, he pointed to a register in the floor directly behind the gentleman in the adjoioiog pew. Looking around the latter could see that there was a hot tire in the furnaje beneath, and yet no heat came up. When a handkerchief was laid over the register it scarcely stirred. The visitor asked the sexton : "Have you any meahs of ventilation?" "No, sir." " Are there no windows open ?" " None whatever." " How then can you ezpect the air to come in here if' it can't get out somewhere?" There was no reason - the man was nonI'lussed. "Did you ever try to blow in a buttle?" continued the inquirer. "No, sir." " Do you think if you did, that you could force any more air into a bottle by blowing than was in it before?"- He couldn't say. Never had thought of it. " Welt," continued the gentleman, "you would Boon find out, if you tried, that it was impossible, and neither can you force air into this churcu through a register if you don't open a window or some othcr erfice. " "But," the sexton demurred, "opening a window would let in the cold air, wouldn't it?" "You just try it," was the response. " Raise some of the wiudows on the leeward side of the church, and see what will happen." It was done, and instantly the handkerchief lying op the register rose half way to the ceiling with the force of the apcending current. The sexton stood aml stared in astonishment.