a7id Functions of the Spo7ige. 141 



and expands. Cj The part where the white base commences, 

 and where the ciliae seem to terminate. 

 Fig. 29. Appearance of the young Spongia panicea, after the 

 ovum has fixed and spread for fourteen days on a watch-glass. 

 a, Central opaque part to which the spicula were at first con- 

 fined, b, Transparent homogeneous margin by which the 

 young sponge spreads, and which likewise produces spicula. 

 Cy Halo of accumulated sediment frequently seen round the 

 margin, at a little distance from the young sponge, and inclos- 

 ing a cleared space, as in Fig. 27. d. The part where the mo- 

 nade-like parenchymatous matter terminates, and where the 

 colourless homogeneous matter commences. 



Enumeration of the Instruments requisite for Meteorological 

 Observations ; with Remarks on the mode of conducting such 

 Observations. By Professor Leslie. 



XliVERY meteorological observatory, if it shall register with 

 accuracy, and in a complete and satisfactory manner, the various 

 atmospheric phenomena, ought to be provided with the follow- 

 ino^ instruments. 



1. The barometer, which measures the pressure of the atmo- 

 sphere ; 2. The thermometer, which indicates its degree of beat ; 

 3. The hygrometer, which marks its relative dryness ; 4. The 

 atmometer, which measures the quantity that evaporates in a 

 given time from the surface of the earth • ; 5. The photometer, 

 which indicates the intensity of the light transmitted from the 

 sun, or reflected from the sky ; 6. The cethrioscope, which de- 

 tects the cold showered down from the chill regions of the high- 

 er atmosphere ; 7. The cyanometer, which designates the grada- 

 tion of blue tints in the sky ; 8. The anemometer, which mea- 

 sures the force and velocity of the wind ; 9. The ombrometer or 

 rain-gauge, which marks the daily fall of rain, or baill, or snow ; 

 10. The electrometer, which indicates the electrical state of the air ; 



* In a close room or sheltered in external air, the atmometer might supply 

 the place of an hygrometer ; and compared with another one freely exposed, 

 it might serve as a substitute for the anemometer. 



