to getat the charcoal and so expel the oxygen there. Thisspiral ventilator was invented by Mr. Latham, and isalso manufactured so as to allow of fixing upon thesummit of any ventilating pipes. (See also fig. 32a.) Sewers. Very little need be said concerning sewers, as theyare under the especial… … to lay in the bottom with what are called inverts.These are sketched at fig. 35, and are shown in theirplaces at figs. 36 and 37. Where the drain-pipes of ahouse enter the main sewer, flap-traps similar to fig. 38are fixed in the sewer-walls. A square one, forinstance, is shown in the sewer at fig.…
