1 43 Military Rockets. — Sandstone. — Magnetism. 



attempt has ever been made, to give them motion round their 

 longitudinal axis in their progress through the air, similar to a 

 rifle ball or arrow, thev will much oblige me. 



Query — Could the required motion be given by attaching two 

 or more narrow slips of thin iron, in a spiral direction, on the 

 case, similar to tiie feathers on an arrow, but placed on the con- 

 trary end, or by forming two holes diametrically opposite at the 

 anterior end, on the same principle as Dr. Barker's mill, or as 

 fire-works are sometimes exhibited whirling on their axis? So 

 far they would differ, that those have only a circular motion, the 

 rocket should have that combined with its progressive motion : 

 no doubt some portion of the impelling matter would be diverted; 

 consequently the range shortened : even with this deduction, the 

 certainty of the flight might be more than a compensation. 

 I am, sir, 



Your most obedient, &c. 

 I. K. K. 



MILITARY ROCKETS. 



Baron de Zacli announces, that Capt. Schumaker (brother 

 of the Astronomer Royal, Copenhagen) has invented a rocket 

 superior to Congreve's both in force and in the precision with 

 which they are thrown. A new corps has been formed to use 

 these missiles. They ascend to an immense height, and then 

 exhibit a globe of fire, which may be seen at a distance of se- 

 venty miles. . 



SANDSTONE OF CAITHNESS, &C. 



To Mr. Tilluch. 



January 1, 1820. 

 Sir, — In my work on the Western Islands of Scotland, I hare 

 suggested (vol. ii, p. 104) that the sandstone of Caithness was 

 similar to that of the western coast of Ross and Sutherland, and 

 have also questioned whether that of Cromarty and Aberdeen- 

 shire does not belong to the same species. Since that book was 

 printed I have had an opportunity of examining the districts in 

 question ; and, that I may not mislead future geologists, I beg 

 to say that the last of these suggestions is unfounded, and that 

 I have not as yet been able to satisfy myself respecting the geo- 

 logical relations of the sandstone of Caithness. It is not in my 

 power at present t j enter into the details necessary for elucidat- 

 ing this subject. I am, sir, 



Your obedient servant, 

 J. MacCullocii. 



ISLE OF ELBA. — MAGNETISM. 



Baron de Zach announces in his *' Correipondence" vol. i» 

 that the opinion long entertained, that the Isle of Elba, from the 



quantity 



