Prof. Ehrenberg's Researches on the Infusoria. ^25 



above mentioned nervous circle in the Hydatina ; and it is very- 

 probable that the two filaments, which in the latter animal are 

 sent forwards from this ganglion, or even the ganglion itself, 

 subserve the purposes of vision. The number, disposition, 

 and colour of these points is the same in the Eosphora nqjas, 

 where the mesial eye is still larger and more distinct. In the 

 Philodina erythrophthalma their colour is the same, but they 

 are only two in number, (the most common disposition in this 

 class), much smaller, and situate more posteriorly. In the 

 Lepadella avails one only is visible of considerable size in the 

 mesial situation of the large one of the Eosphora *. 

 f To be concluded in our next Number.) 



Plan for Cooling Rooms and Ventilating them in Tropical Cli- 

 mates. By Captain Robert Watjchope, R. N. Commu- 

 nicated by the Author. (With a Plate.) 



JN oTHiNG can be more sinlple than the plan adopted for warm- 

 ing houses in cold climates by means of heated air, to accom- 

 plish which requires no mechanical process whatsoever. 



The reverse, however, is more difficult, viz. the cooling and 

 ventilating houses in warm climates, where the air in the inte- 

 rior of the house is always cooler than that which is outside. In 

 the dead calms of the tropics this can only be effected by me- 

 chanical means, first cooling the external air, and then forcing 

 it into the room by pressure. In India, indeed, the punka is 

 used ; but this machine does not change the air in the room, 

 being merely a large fan, and is of no service for ventilating, 

 which is the great desideratum for soldiers' barracks and hospi- 

 tals, &c. 



The plan I propose for this purpose, which is shown by the 

 accompanying model and drawing (PL IV. Fig 1.), is as follows: 



The pipes, which should be of about six inches in diameter, 

 are made of porous earthenware, and are connected by bent 

 pieces to their ends, as seen in the model, so that a blast of air 

 may pass freely from the lower pipe in connection with the bel- 

 lows or funnel, to the uppermost, which conveys it into the 

 • The Plate illustrative of Ehrenberg's discoveries will be given in nejtt 

 Number of Journal, along with the conclusion of the article 



