72 



but that both are not necessarily implicated ; and that, in fact, cases 

 occur where there are marked deviations from what may be consi- 

 dered the more common occurrence. Having observed such cases, 

 and not being aware of any satisfactory explanation, the author ex- 

 amined with care the continuation upwards of the anterior and pos- 

 terior columns of the spinal marrow into the medulla oblongata and 

 found that the decussation at the upper part of the spinal marrow 

 belonged in part to the columns for motion, and in part to the 

 columns for sensation ; and farther, that the decussation is only par- 

 tial with respect to either of these columns ; thus elucidating by the 

 observation of the actual structure what before appeared very un- 

 satisfactory in pathology, and anomalous in disease. 



The paper is illustrated by drawings made from the dissections of 

 the author. 



*' Description of a self- registering Thermometer and Barometer in- 

 vented by the late James Coggan, Esq., and bequeathed by him to the 

 Hoyal Society." By Roderick Impey Murchison, Esq., F.R.S., 

 V.P.G.S., &c. 



The self-registering thermometer used by Mr. Coggan is of Six's 

 construction, and consists of a siphon tube, open at one extremity, 

 and operating by the expansion and contraction of a large body of 

 spirit pressing on a column of mercury in the lower bend of the tube. 

 On the other side of the wooden frame to which this thermometer is 

 fixed, a siphon barometer is attached ; and both these instruments are 

 made to act on iron-floats suspended by a thread, and counterpoised 

 over a pulley. Transverse wires are affixed to these threads, and are 

 forced against a sheet of ruled paper on a frame, which from its 

 connexion with a clock is advanced a certain space each day, by a 

 spring hammer forming part of the striking machinery of the clock. 



" On the action of light upon the colour of the River Sponge." 

 By John Hogg, M.A., F.L.S., C.P.S., &c.. Fellow of St. Peter's Col- 

 lege, Cambridge. Communicated by Thomas Bell, Esq., F.R.S. 



The author found that the green colour of the Spongilla fluviatilis, 

 or river sponge, is acquired solely through the agency of light, and 

 is lost when the sponge is removed from its influence. As this does 

 not appear to be the case with Actiniae, the Hydra viridis, or any 

 other Polype, the author is disposed to consider this production as 

 being nearer allied to the Algse or Fungi, than to any tribe belonging 

 to the animal kingdom. 



" Researches on the Tides. Ninth Series. On the deduction of 

 the Laws of the Tides, from short Series of Observations." By the 

 Rev. W. Whewell, M.A. Trin. Coll., Cambridge. 



It is very desirable to ascertain whether it is possible to deduce 

 the laws of the tides from short series of observations ; since, if it 

 be so, not only does the construction of good tide tables for differ- 

 ent places become more easy ; but also the value of tide^ tables is 

 much increased, if the predicted tides agree with those of each year 

 as well as with the mean of many years. The object of the author 



