160 Hutoi'ij of Mechanical Inventions, and 



10. On the great Power and Duty of some new Steam Engines. 

 Our mechanical readers are aware that the power of a steam engine is 

 measured by the number of pounds of water that it will lift one foot high 

 by each bushel of coals consumed. Hitherto the best engines have been 

 able to raise only 40,000,000 lbs. of water one foot high by means of one 

 bushel of coals. An improvement, however, has been made by Captain 

 Samuel Grose, which increases their power without any additional com- 

 plication or expence. 



The first wiiicli he erected was at Wheal Hope with a sixty inch cylin- 

 der, working single as usual. The following was the work which it per- 

 formed : , 



April, 42,101,739 lbs. July, 55,012,292 lbs. 



May, 42,241,650 August, 50,979,084 



June, 54,725,716 



Another engine subsequently erected at Wheal Towan by Captain 

 Grose, having a cylinder of eighty inches, produced the following re- 

 markable effects ; 



April, 61,877,545 lbs. July, 62,220,820 lbs. 



May, 60,632,179 August, 61,764,166 



June, 61,762,210 



Phil Mag. Oct. 1827. 



11. Process for preparing Indelible Writing-ink. 

 Make a saturated solution of indigo and madder in boiling water, and 

 in such proportions as to give a purple tint ; add to it from one-sixth to 

 one-eighth of its weight of sulphuric acid, according to the thickness and 

 strength of the paper to be used. This makes an ink which flows pretty 

 freely from the pen ; — and when writing which has been executed with it 

 is exposed to a considerable but gradual heat from the fire it becomes 

 completely black, the letters being burnt in and charred by the action of 

 the sulphuric acid. If the acid has not been used in sufficient quantity 

 to destroy the texture of the paper and reduce it to the state of tinder, the 

 colour may be discharged by the oxymuriatic and oxalic acids and their 

 compounds, though not without great difficulty. When the full propor- 

 tion of acid has been employed, a little crumpling and rubbing of the pa- 

 per reduces the carbonaceous matter of the letter to powder ; but by put- 

 ting a black ground behind them they may be. preserved, and thus a spe- 

 cies of indelible writing-ink is procured, (for the letters are in a manner 

 shaped out of the paper) which might be useful for some purposes; per- 

 haps for the signatures of bank notes. — Brande's Journal. 



12. Observations on the Explosion of Steam Boilers. By Mr W. J. Hen- 



:> 1 WOOD. 



In the Annals of Philosophy for June 1827 Mr Henwood has published 

 some interesting observations on Mr Taylor's opinions respecting the cause 

 of the explosion of steam boilers, which were reprinted in our Journal, 

 No. xii. p. 335. 



