Page:Popular Science Monthly Volume 50.djvu/29

Rh sacrificed on this account, for the concreted bottom of the tank may be made to slope downward from the base of the glass plate till the needed depth is reached. Nor does the similarity in the various aquariums extend only to the corridor to which the general visitor is admitted. In their internal arrangements an even more strikingly similar ground plan is found to prevail. In all cases the attempt has been made to keep from the mind of the visitor the idea that water pipes, pumping engines, and blouse-wearing attendants—none of which withal are oppressively tidy—are necessary to the well-being of the tanks. And it is for this reason especially that the region behind the tanks is usually kept from profane eyes. Dark passageways lead to it, shielded



by hidden doors, and one who enters, coming from the dusky corridor, is at first blinded with a flood of light. Above him is the glass roofing of a conservatory, and sunshine is pouring down upon the rock work of the tanks, thence to be reflected into the public hall. At his feet extends a concreted pathway; on either side are the tanks, or more strictly rock-lined pools, at whose farther ends can be seen the glass plates through which, in the corridor, the visitors are gazing. Above and around are serpent-like pipes, stretching at full length, abruptly coiling as they dip to the water surface or pass downward below the floor, a confusing maze, bubbling and hissing with steaming water. The system in the management of the water supply becomes, however, clearly understood when the mystery of strangeness has passed away. It has merely to conform to the hygienic law of its