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Dreams, are carried on independently of any exertion of the will. 

 ^""V"" Mis second argument is, that if the influence of the will 

 during sleep be suspended, the mind should remain pas- 

 sive; and that this is the case in i.\r dreams, has al- 

 ways been considered " as one of the most extraordi- 

 nary circumstances with which they are accompanied. 

 It is indeed a matter of vulgar remark, that our dreams 

 are in every case involuntary on our part ;" not that we 

 do not exert volition in our dreams, especially, as has 

 been already stated, to remove unpleasant images, but 

 that the influence of ot.r will is then suspended. Be- 

 sides, Mr Stewart argues, that, if his opinion be well 

 founded, the concepli-ms which we form during sleep 

 of sensible objects, will l>e attended with a belief of 

 their real existence as much as the perception of the 

 same objects is while we are awake ; and this is an un- 

 doubted and well known fact. (Stewart's Philosophy 

 of the Human Mind, 4to edit. chap. v. sect. 5.) 

 'Jen. 11. Cullen was the first who pointed out the constant 

 and regular resemblance between dreams and delirium ; 

 and who proved., that, at the commencement, and du- 

 ring the continuance of sleep, the different senses and 

 organs sleep successively, and in ;i very unequal degree; 

 and that the partial excitation of those parts of the brain, 

 which correspond to them, by disturbing the harmony 

 of its functions, produces irregular and confused ideas, 

 which have no foundation in reality. This doctrine of 

 Of CabanU. Cullen has been adopted by Cabaiiis, who enters into 

 it more minutely and fully. As his remarks on the sub- 

 ject are, we believe, very little known in this country, 

 we shall conclude this article by a brief abstract of 

 them, so far as they regard, and in his opinion explain, 

 the phenomena of dreams. Before, however, we give 

 hi- observations on dreams, it will be proper to attend 

 to what he says respecting sleep. In illustration of 

 Cullcn's doctrine, that the senses and organs fall t. 

 successively, he observes, that the muscles which move 

 the arms and the legs relax, and cease to act, on the 

 approach of sleep, before those which sustain the head ; 

 and these before those which support the back. At 

 the period when the sight, under the protection of the 

 rye-lids, no longer ivr<-i\es impressions, all the other 

 senses proser\ e their sensibility entire : the sense of 

 : ing doe* not fill asleep, till after the sense of taste; 

 the hearing, till after the sense of smelling; and the 



of touch after the hearing. This last sense appears 

 to be awake, even during the most profound sleep; for 



orcise it, when we change ourjinsition in bed, which 

 often takes place without in the smallest degree disturb- 

 in? our sleep. Nor do the senses sleep equally pro- 

 foundly. The scn>es of taste and smelling awake the 

 :he sight seems to awake with more difficulty than 

 the hearing ; the smallest noise will sometimes awake 



uuh'ili-t--, on whom the most vivid light makes 

 no brpresaon, though their eyes are open. The sleep 

 of the sense of touch i- more easily disturbed than that 

 of the healing; the same person who would not be a- 

 waked by noises very sudden and loud, starts up imme- 

 diately if the soles of his feet are tickled in the slightest 

 degree. The same is the case with respect to the in- 

 ternal organs ; the viscera fall to sleep one after the 

 other, and sleep with different degrees of profoundness. 

 The truth of these observations, Cabaiiis confirm 

 what happens to somnambulists, and cataleptic patients. 



o n-i,iarl>. that in different persons the different 

 muscles seem to fall to sleep at different perimls : some 

 can s!e p on horseback ; with them the voluntary pow- 

 er over the muscles of the back is retained and exerci- 

 *d during sleep : others sleep standing, or even while 



they are walking. Hence this author infers, that vo- Dreatns,- 

 lition exists and is exercised during sleep ; and the I^ud^i rig. 

 exercise of it he thinks is further proved by the facts, "*"Y~^ 

 that a person while in this state puts up his hand to 

 drive away the fly that may have settled on his face ; 

 pulls the bed-clothes upon him ; and, as was before ob- 

 served, changes his position in bed. But besides these 

 facts respecting the successive order, and the different 

 degrees, in which the organs and the senses sleep, 

 there is established among them, while they are in this 

 state, new sympathies and relations, with respect to the 

 impressions which peculiarly belong to them. Hence 

 their influence on the brain is different from what it is 

 when we are awake ; thus, the process of difficult di- 

 gestion gives rise to different images in the brain during 

 sleep, from those which it would produce in our wak- 

 ing state. 



Having premised these observations, Cabaiiis next Opinions of 

 enquires, by what kind of impressions, and by what Cabni. 

 state of the animal economy, are dreams produced ? To 

 this he replies, that they evidently take place when the 

 action of the external senses is Mispended : that of most 

 of the internal organs moderated, but in a different de- 

 gree ; the sensibility of some of them being even in- 

 creased : in this state, a large portion of the nervous in- 

 fluence is concentrated in the brain, which is given up 

 either to its own peculiar impressions, or to those which 

 it receives from the internal organs, which still exert 

 their influence without the intermixture of impressions 

 from external objects, which might give them order and 

 consistency. The compression of the diaphragm on the 

 process of digestion often recals, in our sleep, forgotten 

 events, or persons, or trains of reasoning, by acting on 

 that part of the brain where the impressions of these 

 objects were formerly excited ; for it is not true, that 

 our dreams relate only to those things which have ex- 

 cited our attention or interest while we are awake. Such, 

 no doubt, from the power of association, very frequent- 

 ly give rise to them ; but in many cases they can be 

 accounted for only on the supposition that the brain, 

 (luring sleep, is given up either entirely to its own pe- 

 culiar impressions, or to those impressions which are 

 excited or modified by the action of such organs as still 

 retain their power. On this theory we shall only re- 

 mark, that even if it is quite intelligible and satisfactory 

 to the physiologist, it will not be received with much 

 deference by the metaphysician. See Rapports du I'/iy. 

 sique, et du Moral de I' Homme, par P. j. G. Cabanis, 

 torn. ii. p. 504551. (w. s.) 



DREDGING, is an operation of the utmost conse- 

 quence to the improvement of navigable canals, rivers, 

 docks, harbours, &c. and is performed by means of 

 machines, of various constructions, so contrived as to 

 loosen and lift the mud, gravel, or other materials, which 

 are occasionally deposited, or may have been the origi- 

 nal stratum, under water. 



As much depends on local situation with regard to 

 dredging machines, like many other branches of civil 

 engineering, it is difficult to give precise information on 

 tin- subject, and a great deal must be left to the persons 

 who arc intrusted with the immediate direction of the 

 works to be performed. 



We shall endeavour, however, to give such general 

 ideas, and accompany these with drawings of one of the 

 most improved and powerful machines now in use in 

 this kingdom, as, we hope, will render this article very 

 valuable to the practical engineer. 



We believe dredging under water was first resorted nri r 'n of 

 to by the Dutch, for clearing the bars or entrances to d"* ! gi n g. 



