HYDROSTATIC FUNNEL.--This is represented by pl. 3, fig. 31. It is an instrument of constant use in chemical experiments. Form a funnel at the extremity of a tube in the manner described above, having previously blown a bulb near the middle of the tube. When this has been done, bend the tube into the form shown by the figure. * * * * * HOUR-GLASSES.--Blow four bulbs on a tube close to each other; open the two end bulbs like funnels, and then form them into flat supports or pedestals, according to the method described at the article _Test-glass with a foot_. Obstruct entirely the canal which separates one of these feet; choke to a certain extent the passage between the two remaining bulbs; and close the canal between the other foot and the bulbs, after introducing the quantity of sand which you have found to be necessary. See pl. 3, fig. 13. * * * * * HYDRAULIC RAM.--This instrument is represented by pl. 4, fig. 15. Employ a tube about six feet long, with thick sides and of large diameter. Seal it at one extremity, _k_, and border it at the other; solder at _p_ an additional piece, choked so as to receive a valve. Pierce the tube at _l_; draw it out, and fix a funnel there; then twist the tube into a spiral. Form, on the other hand, a fountain of compression, _o_, and a funnel, _m_; and fix both of these pieces by means of sealing-wax, as soon as the two valves _p_ and _l_ have been put into their places. * * * * * HYDROMETERS.--_Hydrometers_ are instruments which, on being plunged into liquids, indicate immediately their density or specific gravity. _Areometers_ differ from hydrometers sometimes in graduation, sometimes merely in name. The following are examples of hydrometers, of which a great many varieties are in use. * * * * *