58 Transactions of the American Institute. 



This process is without precedent. The use of sand in sawing- 

 marble or in grinding glass by common methods hardly furnishes an- 

 analogy. 



The apparatus consists of a tube of small diameter concentrically- 

 placed within a somewhat larger tube, and connected, the former with. 

 a reservoir of sand and the latter with a generator of high steam. 

 The vessel of sand being placed higher than the mouth of the tube,, 

 its contents discharge themselves by their gravity ; but on the admis- 

 sion of steam to the outer tube, the discharge is accelerated by aspira- 

 tion or exhaustion, while the sand discharged is driven in a forcible 

 current against the surface to be acted upon. The distance of this 

 body from the jet is greater or less, according to the object to be 

 effected. "When mere surface cutting or depolishing of glass is 

 desired, an air blast with a pressure not exceeding four inches of water 

 is employed. A fan suffices to produce this ; and the jet, instead of 

 being cylindrical, is a broad and thin sheet. The fan, occupying the 

 lower part of the apparatus, drives the sand through a circuit, in 

 which, on the descending side, it encounters the object to be acted 

 upon, and then, falling further, comes under the action of the fan 

 again, and so continues to be used over and over again. 



The utility of this invention is apparent in the statement above 

 given, of the purposes to which it is applicable. It is regarded by 

 the judges as being one of the most remarkable and valuable inven- 

 tions which the age has produced. 



Considering, therefore, the great originality, importance and value 

 of this process, and the great variety and diversity of applications, 

 both useful and ornamental, of which it is capable, the judges unani- 

 mously recommend that the great medal of honor of the Institute be 

 conferred upon the ingenious inventor, as a well merited distinction. 



F. A. P. BARNARD. 

 ALFRED H. MAYER. 

 HENRY MORTON. 



Professor Egleston, of Columbia College, made experiments with 

 the sand-blast, the results of which are given in the following letter: 



New York, November 13th, 1871. 

 Chas. "Wager Hull, Esq.: 



Dear Sir. — I inclose the results of the experiments which I made 

 at the fair of the American Institute, on the effect of the sand-blast 

 on substances of different hardness. I give below the loss in weight 

 and the time required to effect it : 



