1846.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



369 



EARL'S GONIOMETRICON. 

 CRegistered lij Mr. George Earl, School of Design, Peckham.*) 



The grnat recommendation which this instrument has received from the Pictorial Times induces us to lay it before our readers, 

 be found to be a very serviceable appendage to the travelling architect, 



We doubt not it will 

 The following is a description of the instrument as given in the above 



journal. F'B. '• 



"This neat, elegant, and portable delineator has been con- 

 trived to enable persons unskilled in drawing to find the perspec- 

 tive direction of the vanishing or receding lines of objects. 

 This it does with an ease and accuracy which is almost fascinat- 

 ing. All practitioners, and persons in the habit of sketching 

 architectural or other complicated views, know the extreme diffi- 

 culty of getting the leading lines of the picture projected with 

 accuracy, and how easily the subordinate parts fall into their 

 places when once these are obtained. This difficulty the gonio- 

 nietricon obviates, and with its assistance the most uninitiated 

 may hereafter master the art of drawing in correct proportionate 

 perspective. The mode of using the instrument is thus described 

 by Mr. Earl: — Place the instrument between the eye and the 

 object to be outlined, which is done by holding it with 

 the finger and thumb of the left hand, at a point between the 

 top of the arc and the universal joint. It is then fixed in that 

 position at an angle of 00 degrees with the line of vision, a task 

 accomplished by taking a small ivory acorn attached to the in- 

 Btrument by a string, and placing it firmly between the teeth, 

 ■wben the connecting string is stretched to its fullest tension. 

 This done, the instrument is moved till one of the indicators 

 (which in the cut looks like the hand of a clock,) coincides with 

 .the line whose downward or upward direction it is sought to 

 ascertain. That point discovered, the instrument is laid flat on 



the drawing-paper with the horizontal bar parallel with its lower line, and gently moved to the required position, when the line of direction is ruled off 

 from the edge of the indicator. The bottom of the instrument is set with divisional points, to assist in sketching the proportions of figures, trees, and 

 objects of irregular form or outline. 



•' We have only to add to our recommendation of the goniometricon, that it is much used by artists and travellers, and recommended to general use 

 by no less a person than the .Astronomer Royal." 



The Engraving, fig. 1, is a front view of this very ingenious and useful instrument; fig. 2 exemplifies the manner of its application. 



Besides the valuable testimonial referred to, from Professor Airey, we observe there is one from IVlr. Reynolds, of the Kew Observatory, who says — 

 " Tour instrument is precisely what Dr. Priestley, in his valuable work on perspective, hoped some mechanical man would discover, in order to make 

 the science of perspective tangible to the comprehension of all." Fig. 2. 



* We are indsljted for the use of the wood engravings to our eotemporary, the " Mechanics' Magazine." 



BLASTING UNDER WATER. 



Paper on the application of Gunpowder as an instrument of engineering 

 operations, e-remplified by its use in blasting marl rocks in the River Severn. 

 By George Edwards. Read at the Institute of Civil Engineers. 



Many plans have been proposed at different times for the improvement o' 

 the Severn. It is sufficient, however, for the present purpose to state, th a' 

 in 1842 an Act was obtained under the advice of Mr. W. Cubilt, V.P. Inst. 

 C.E., fur the improvement of 43 miles of its length, from Stourport to 

 Gloucester; over which distance, in many places there was not 2 feet depth 

 of water during the summer season. The object of the proposed works i 



to increase this depth to 6 feet of navigable water during all seasons. Above 

 Worcester the additional depth is obtained partly by dredging, but chiefly 

 by a series of four weirs, varying between 300 and 400 feet in length, with 

 side locks for the the traffic. Between Worcester and Gloucester (a distance 

 of 29 miles), it is proposed to obtain the required depth, partly by contrac - 

 ing the channel by embankments of fascines, and partly by dredging. Messi 

 Grissell and Peto having undertaken the entire completion of the works, 

 from Stourport to Gloucester, the superintendence of the dredging oj. r. 

 tions was entrusted to the author. The shoals to be removed by dr.dging 

 are generally isolated, varying from 100 yards to half a mile in length, and 

 they require excavating to a depth of from 3 to 5 feet. A large proportion 



4tj 



