SCIENCE 



Friday. March 10, 1905. S„"..'^S.i'pS, ...«, . 



OlFFRaeTI©N GrHTINGS 



Gratings Ruled on Rowland's Engine 



S 53. Rowland Grating, plane, 15000 lines to the inch, ruled surface 0.9 x 1.03 inch. 



Grade A • $30.00 



S 54. Ditto, Grade B . . . 25.00 



S 55. Rowland Grating, plane, 15000 lines to the inch, ruled surface 1.5 x 1.75 inch. 



Grade A 60.00 



S 56. Ditto, Grade B 50.00 



Prices of larger sizes of plane and concave gratings given on request. 



kves* Replicas of Rowland Gratings 



S 111. Ives' Replica of Rowland G-ating, about 15050 lines to the inch, ruled surface 



about one inch square $6.00 



S 112. Ives' Replica, ruled surface 1 3-8, x 1 7-8 inch 12.00 



S 113. Ives' Replica, ruled surface 1 3-8x1 7-8 inch, special selection, mounted under an 



optically plane cover glass 15.00 



S 115. Circular Grating, 5000 lines to the inch, for lantern projection. Gives a complete 



circular spectrum 5.00 



Circular describing these new process replicas will be sent upon request. 



Wallace's Replicas of Rowland Gratings 



S 21. Wallace Grating, 1 x 3-4 inches, 14,438 lines to the inch, first quality $5.00 



S 22. Wallace Grating, 1 x 3-4 inches, 14,438 lines to the inch, second quality 3.00 



S 95. Wallace Grating, 1 3-4 X 1 3-8 inches, 15.000 lines to the inch, first quality . . . . 8.00 



S 96. Wallace Grating, 13-4x1 3-8 inches, 15,000 lines to the inch, second quality 5.00 

 S 125. Wallace Grating, 14,438 lines to the inch, mounted for direct vision on prism with 



face 1-2 inch square . 6 50 



S 126. Wallace Grating, 1 x3-4 inches, 14,438 lines to the inch, mounted for direct vis- 

 ion on prism with face 1 1-4x1 inches 9.00 



S 127. Wallace Grating, 1 3-4x1 3-8 inches, 15,000 lines to the inch, mounted for direct 



vision on prism with face 2 1-8x1 5-8 inches 16.00 



Rowland's Photographic Map of the Normal Solar Spectrum 



S 37. Series often plates, wav lengths 3000 to 6950 $20.00 



THE SeiENTlFie SHOP 



ALBERT B. PORTER 



Scientific Instruments 322 Dearborn St., enieaG© 



