846 Mr Carmichael on Water as a 
fecal orifices, for we might suppose, that, while one part of the 
animal dilated by its own elasticity to inhale water through the 
small superficial pores, other parts might be contracting to con- 
vey the streams along the internal canals, and propel them 
through the fecal orifices. It would likewise enable us to ac- 
count for the shrinking motion of this animal, when roughly 
touched by the hand, or beaten by the winds and tempests, 
which was ascribed to it by some of the Greek naturalists. Or 
if the sponge could be satisfactorily shown to possess no such 
contractile power, or to possess it only in so low a degree as to 
afford no explanation of its living phenomena, our researches 
would then be necessarily directed ’to a new object ; we would 
then have to inquire into some mysterious causes of the currents, 
totally independent of any general motions of the mass of the 
animal, and would thus have advanced one step nearer to the 
truth by limiting the object of our inquiry. 
( To be continued.) 
Art. XVII . — On Water as a Moving Power for Machinery . 
By C. Carmichael, Esq., Engineer, Dundee. 
I observe in the Philosophical Journal for last month, a pa- 
per on the advantages of a Reservoir at the head springs of the 
Water of Leith, for the better husbanding the annual supply of 
water which that river affords. 
I have been much impressed with the advantages which would 
accrue to the manufacturing districts of this country, could 
means be adopted to turn a large portion of the rain that falls 
on our uncultivated hills to the purpose of driving the machinery 
of our manufactories, improving the means of inland navigation, 
and preventing, or at least checking, the destruction of our cul- 
tivated valleys, by uncontrolled floods. 
It is no uncommon thing in this country to see the hopes of 
the husbandman, with the bridges and mill-wears of our rivers, 
all swept away by the mountain-torrent, in one desolating hour, 
when properly regulated reservoirs, of sufficient extent, would 
not only, in a great measure, prevent the destruction of much 
valuable property, but would store up the fertilizing showers of 
