120 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[April, 



fallier of Mr. David Stovciison being universally known as the engineer 

 of tlie Bell Rock Light Honse, and many other important works. 



On' attentivelv examining this book, we find that our expectations 

 have been amplv realized-we tind it to be the production oi one who 

 thoroughly understanding the subject on which he writes, falters not, 

 hesitates not, shrinks not from writing freely for fear of exposing his 

 io-norance, resorts to no paltrv expedients for filling up Ins book with 

 mere words enveloping ideas like needles in hay, but who, in a clear, 

 lucid, easv, and familiar style describes the maimer of conducting the sur- 

 vey of a r'iver or harbour, "from beginning to end. The tirst two chapters 

 are devoted to triangulation, and to the choice and measurement ot a 

 base line. It seerns from these that the author adopts the method of 

 connecting the two banks of the river by a series of angles taken from 

 each station. The stations are at short distances from each otiier, 

 and the construction lines of the survey change their direction at 

 every station. Thus no line along the banks of the river is longer 

 than the distance between two of the principal stations ; and thus, 

 when the construction lines are laid down, they form a series ot Ui- 



angles erected on each base from station to station, and having their 

 vertices in opposite stations on the other side of the river. 



It is wel 

 known to most of our readers, that there are various methods of 



arrano-ing the construction lines m surveying; and the one which is 

 most strictly correct in a Geometrical sense is undoubtedly that in 

 ■which the whole woik is enclosed by some large triangle, or at least 

 entirely intersected by one or more straight lines, on which triangles 

 are constructed as large as the extent of the work may require. 1 he 

 beautiful accuracy with which all the parts of a survey executed in 

 this manner fit into each other ; the strict tying of the work together; 

 the admirable system of proofs and checks alfbrded : and the distri- 

 bution of minute error arising from imperfect chaining, while any error 

 of consequence is at once discovered at the precise spot where it 

 occasions distortion;— all point out the method of surveying within 

 loni' construction lines as the verv best that can be adopted tor ail 

 ordtnarv surveys of land. But in the case of rivers and coasts tnere 

 are maiiy practical objections to this method, arising from the diftculty 

 of measuring long straight lines on the shore or margin sufficiently near 

 the water to furnish the necessary offsets, and from the impracticability 

 of measuring the numerous lines which would be required across the 

 river, or which would be required to extend out to sea, supposing the 

 system followed in the survey of a single line of coast. Hence in 

 marine surveys the necessity of employing the theodolite or some 

 other instrum'ent for measuring angles is universally admitted ; and 

 this point being settled, the next consideration is that of determining 

 the form and position of the series of triangles which, depending on 

 each other and constructed in the manner of a continuous net or frame- 

 work, constitute the basis for finding the main points and hlling up the 

 ■whole detail of the survey. The two first chapters afford some useful 

 practical information, -as to the best method of observing the angles 

 and constructing these important lines. 



The third chapter is devoted to tide observations, the author 

 strongly insisting on the importance of these being correctly made at 

 many different points, in consequence of the irregular level assumed 

 by tiie tide wave at dift'erent parts of its course up the river. Some 

 very curious and important details are given in this and the following 

 chapter on soundings, relative to the inclined surface presented by the 

 water in tidal rivers at different times of the tide. Thus in the nver 

 Lune, the current of which runs from Lancaster to Glasson, the level 

 of low water during a spring tide was found to be 11 ft. lower at the 

 latter place than at Lancaster. Also -at the same instant of time, when 

 it was low water at Lancaster, the level of water at Glasson was 4 ft. 

 4 in. above low water mark at Lancaster. On the river Dee the level 

 of low water mark at Flint was 7s ft. below the low water mark of the 

 .same tide at Connah's Quay, only 21 miles higher up the river. And 

 at the moment of low water at Connah's Quay, the water at Flint was 

 5A ft. above low water mark at Connah's Quay. These are only a few 

 examples of the irregularity of level presented by the surface of water 

 in tide rivers : in the course of the book there are many such examples, 

 extending through both spring and neap tides. They prove in the 

 most decided manner— 1st. that it is an egregious error to assume the 

 low water mark at different points on the same river to be on the 

 same level ; and, 2nd. that it is almost equally erroneous to suppose 

 that at any given instant of time the level of water in a river is the 

 same at two distant points. A difference of level, also, prevails in the 

 high water mark of the rivers Dee, Lune, and Forth, from all of which 

 actual observations are detailed; but this difference is not to such an 

 extent as that in the level of the low water marks, although in other 

 livers it is possible that the line drawn through the high water marks 

 of the same tide may be as much inclined as the line drawn through 

 the low water marks." We have not unfrequently seen cases of disputed 

 levelling, only in consequence of erroneous ideas as to the contem- 



poraneous level of tide water, and as to the level of high and low water 

 mark at different points of a river ; and douhts have often been thrown, 

 in consequence, upon the accuracy of a section taken across a district 

 of country, from one point of a river to another, or even from one river 

 to some "other river in another part of tl.e country. The faith of 

 engineers, however, in the ancient errors with regard to the tides 

 wliich we have mentioned, has been already somewhat shaken, and 

 the practical information contained in the book before us will, we 

 trust, explode them entirely, even if it should fail to establish any 

 sound theory on the niins of the old hypotheses. 



In the Stli and Glh chapters Mr. !Stevenson resumes the subject of 

 the actual survey of the river, treating first of the low water survey, 

 which embraces the sand banks, shoals, and other parts of the bed, 

 which are dry at low water, and then of the high water margin, the 

 method of proceeding to the best advantage bei:-g pointed out as to 

 both these parts of the survey. We regret that our space wil not 

 admit of an extract sufficient in length to do justice to the author s 

 views and explanations in this part of the work ; we must, therefore, 

 refer our readers for further information to the book itself. 



The next chapter, on cross sections and borings, is interesting and 

 useful, as exhibiting the most direct manner of proceeding to make 

 sections across the'river, at places where they are necessary to show 

 the inequalities and structure of the bottom, and to point out the parts 

 to be excavated in order to obtain sufficient depth of water in the 

 channel. Mr. Stevenson justly observes that " much time may be lost 

 in makino- the section? and borings, and erroneous data ma_y be ob- 

 tained if'the operation be not gone about in a proper manner." 



Chapter 8 relates to hvdrometric.d observations, principally on the 

 velocity of currents at th"e surface, and the bed of their course. For 

 the purpose of determining the mean velocity from the observed sur- 

 face velocity, Mr. Stevenson gives the following formula, founded on 

 a rule of De Buat : 



a + ( Vo— 1) 

 y = 4 



where a = the observed surface velocity, and 7 = the mean velocity- 

 sought. . r 1 ,■ 



The concluding chapter, relating to the protraction of the lines in 

 the survey, and of the soundings, completes the subject, and although 

 this part 'is equally valuable, and in its mode of treatment equally 

 practical with the rest of the book, it would convey little or no infor- 

 mation to make isolated extracts from it. The whole, however, is 

 well worthy the attention of every engineer and surveyor engaged in 

 the prosecution of marine surveying, to all of whom it may be said, 

 without derogation of their skill", that however practised or proficient 

 thev may be in this part of the profession, this book is calculated to 

 add to their knowledge of the subject. The work contains numerous 

 plans and sections of rivers, showing the mode of surveying and ot 

 representing the cross sections and borings, also examples of the man- 

 ner of keeping the field books in the different stages of the survey. 



BOOK MAKING. 



Sir— I beg leave tt) trouble you with a few remarks respecting a recent 

 publication, with the view of calling your attention to a highly reprehensible 

 practice, which is now becoming common in this class of works. The prac- 

 tice I allude to is the copying and inserting, in several different publications, 

 the same cuts and impressions. In a small work lately published, entitled 

 " Anglican Church Architecture, &c." naturally supposing that the wood cuts 

 and illustrations (with which the volume is rather copiously furnished) were 

 examples not before published, but had been collected by the author to illus- 

 trate and support the opinions put forth in his work, I w.-is induced to become 

 a purchaser; but on looking over the book, I was much surprised to tiud 

 that almost without exception the cuts, &c. were fac-similies of those pub- 

 lished in a recent work entitled " The Glossary of Architecture." and as both 

 proceed from the same publisher, I have no doubt the same blocks did duty 

 a second time. It may be said that the work I now refer to is small in 

 price, hut the principle is equally bad, whatever may be the cost of the pub- 

 lication ; and I hope that you will, by making instances of this sort of book- 

 making public, prevent a practice so vicious in principle and so hurtful m its 

 effects from becoming general. If persevered in, it cannot fail to destroy 

 that confidence which should always subsist between the author and the 

 purchaser of his work. 



